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A070957
Primes p such that the equation sigma(x) = p has no solution.
1
2, 5, 11, 17, 19, 23, 29, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293
OFFSET
1,1
LINKS
MATHEMATICA
r = Range[300]; Complement[Select[r, PrimeQ], DivisorSigma[1, r]] (* Amiram Eldar, Nov 15 2021 *)
PROG
(PARI) for(n=1, 100, if(sum(j=1, n, if(sigma(j)-n, 1-isprime(n), 1))==0, print1(n, ", ")))
CROSSREFS
The prime terms in A007369.
Sequence in context: A118660 A009770 A132121 * A166744 A080165 A239712
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, May 16 2002
STATUS
approved