OBJECTIVE AND REVIEW OF ALL VERSIONS
Erdős #313; independent attempt, 2026-09-23. Are there infinitely many primary pseudoperfect numbers $M$, satisfying $1/M+\sum_{p\mid M}1/p=1$? I read
313.tex and
313_v2.tex, which repeat the same local congruence restrictions. I test a more flexible recursive move than adjoining the single prime $M+1$.
WORK: EXACT TWO-PRIME EXTENSION CRITERION
Let $M$ be primary pseudoperfect, and let $p,q$ be distinct primes not dividing $M$. Then $Mpq$ is primary pseudoperfect if and only if \[
(p-M)(q-M)=M^2+1.
\] Indeed, substitute $\sum_{r\mid M}1/r=1-1/M$ into the defining equation for $Mpq$. What remains is \[
\frac1p+\frac1q+\frac1{Mpq}=\frac1M,
\] which after multiplication by $Mpq$ is $M(p+q)+1=pq$, equivalent to the factored equation. Positivity in the reciprocal equation forces $p,q>M$. Thus all such extensions are obtained by factoring $M^2+1=de$ into positive integers and testing whether $M+d$ and $M+e$ are distinct primes. They automatically do not divide $M$. For example $M=2$ gives $M^2+1=5=1\cdot5$, yielding $p=3$, $q=7$ and the known solution $42$. For $M=6$, $37=1\cdot37$ yields $7,43$ and $1806$. These are explicit checks of the criterion, not new primary pseudoperfect numbers.
ADVERSARIAL VERIFICATION AND REMAINING GAP
The two new primes must be distinct to preserve the squarefree prime-divisor formula. Merely satisfying the congruences in the supplied versions does not guarantee the reciprocal sum is one; the factored identity is necessary and sufficient for this particular extension. If $M^2+1$ is prime, the only factor pair is $(1,M^2+1)$, requiring both $M+1$ and $M^2+M+1$ prime. There is no argument that successful factor pairs continue indefinitely, and the method need not generate every primary pseudoperfect number. The infinitude problem remains.
SOURCES CHECKED
Both local versions listed above; indexed official entry
https://www.erdosproblems.com/313, checked on 2026-09-23. The extension criterion is proved directly and no claim of literature novelty is made.
FINAL
UNRESOLVED. Two-prime extension is reduced to an exact finite divisor-and-primality test; unbounded successful iteration is unproved.
COMPLETION ESTIMATE
Conservative subjective progress toward infinitude.
COMPLETION: 10%