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A337379
Numbers k for which A003961(k) < 2*sigma(k).
4
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 25, 26, 28, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 44, 46, 47, 50, 51, 52, 53, 55, 57, 58, 59, 60, 61, 62, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 78, 79, 82, 83, 85, 86, 87, 88, 89, 91, 92, 93, 94, 95, 97, 101, 102, 103
OFFSET
1,2
PROG
(PARI)
A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
isA337379(n) = (A003961(n)<2*sigma(n));
CROSSREFS
Cf. A337378 (complement).
Positions of zeros in A337380.
Cf. also A246281, A337382 (subsequences).
Sequence in context: A119675 A253781 A037144 * A121684 A191853 A123093
KEYWORD
nonn
AUTHOR
Antti Karttunen, Aug 27 2020
STATUS
approved