A337382 Numbers k for which A003973(k) < 2*sigma(k).

1, 2, 3, 4, 5, 7, 10, 11, 13, 17, 19, 22, 23, 25, 26, 29, 31, 33, 34, 37, 38, 39, 41, 43, 46, 47, 51, 53, 55, 57, 58, 59, 61, 62, 65, 67, 69, 71, 73, 74, 77, 79, 82, 83, 85, 86, 87, 89, 91, 93, 94, 95, 97, 101, 103, 106, 107, 109, 111, 113, 115, 116, 118, 119, 121, 122, 123, 127, 129, 131, 133, 134, 137, 139, 141

Offset: 1

Author

Antti Karttunen, Aug 27 2020

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..20000
• Index entries for sequences computed from indices in prime factorization
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000203, A003961, A003973.

Cf. A337381 (complement).

Positions of zeros in A337383.

Subsequence of A337379.

Cf. also A246281.

Programs

PARI

A003973(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); sigma(factorback(f)); };
isA337382(n) = (A003973(n)<2*sigma(n));