A193066 Odd numbers N such that numerator(sigma(N^2)/N^2) is a prime.

3, 5, 17, 27, 39, 41, 49, 59, 71, 89, 101, 125, 131, 167, 169, 173, 289, 293, 383, 507, 529, 677, 701, 729, 743, 761, 773, 827, 839, 841, 857, 911, 1091, 1097, 1163, 1181, 1193, 1217, 1373, 1427, 1487

Offset

1,1

Comments

Square roots of the terms of A193065. See there for more comments.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(n) = A000196(A193065(n)).

Mathematica

Select[Range[1, 1501, 2], PrimeQ[Numerator[DivisorSigma[1, #^2]/#^2]]&] (* Harvey P. Dale, Sep 24 2016 *)

Prog

(PARI) forstep(N=1, 1e7, 2, isprime(numerator(sigma(N^2)/N^2)) && print1(N", "))

Crossrefs

Sequence in context: A256439 A256444 A032619 * A193070 A030077 A352568

Adjacent sequences: A193063 A193064 A193065 * A193067 A193068 A193069

Keyword

nonn

Author

M. F. Hasler, Jul 15 2011

Status

approved