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A332458 Odd numbers k, not powers of primes, such that sigma(k) == 2 modulo 8 and sigma(sigma(k)) == 6 modulo 8. 4
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified July 10 00:05 EDT 2020. Contains 335570 sequences. (Running on oeis4.)