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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. 5
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
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
Intersection of A228058 and A332457; intersection of A332456 and A332228.
Cf. also A332445.
Sequence in context: A206617 A252686 A178274 * A204948 A237030 A252809
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 15 2020
STATUS
approved

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Last modified April 18 21:51 EDT 2024. Contains 371781 sequences. (Running on oeis4.)