A332458 Odd numbers k, not powers of primes, such that sigma(k) == 2 modulo 8 and sigma(sigma(k)) == 6 modulo 8.

4041, 5193, 15633, 25181, 25497, 26645, 30249, 36441, 36517, 40817, 47045, 53577, 54513, 85697, 87273, 92889, 93393, 94761, 95913, 97281, 111609, 129681, 136233, 143433, 151713, 161257, 162441, 163377, 165897, 171197, 177129, 210033, 212697, 213849, 222993, 228977, 229833, 232897, 238041, 245673, 246969, 250137, 260577

Offset

1,1

Links

Antti Karttunen, Table of n, a(n) for n = 1..9315

Index entries for sequences where any odd perfect numbers must occur

Index entries for sequences related to sigma(n)

Prog

(PARI) isA332458(n) = if(!(n%2)||isprimepower(n), 0, my(s=sigma(n)); ((2==(s%8)) && (6==(sigma(s)%8))));
(Magma) [k:k in [3..270000 by 2]| not IsPrimePower(k) and DivisorSigma(1, k) mod 8 eq 2 and DivisorSigma(1, DivisorSigma(1, k)) mod 8 eq 6]; // Marius A. Burtea, Feb 15 2020

Crossrefs

Cf. A000203, A000961, A051027.

Intersection of A228058 and A332457; intersection of A332456 and A332228.

Cf. also A332445.

Sequence in context: A206617 A252686 A178274 * A204948 A237030 A252809

Adjacent sequences: A332455 A332456 A332457 * A332459 A332460 A332461

Keyword

nonn

Author

Antti Karttunen, Feb 15 2020

Status

approved