A348741 Odd numbers k for which A161942(k) < k, where A161942 is the odd part of sigma.

3, 5, 7, 11, 13, 15, 17, 19, 21, 23, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157

Offset

1,1

Comments

Differs from A088828 for the first time at n=1080, where a(1080) = 2207, while A088828(1080) = 2205 = A348743(1), the value which is missing from this sequence.

Links

Antti Karttunen, Table of n, a(n) for n = 1..16291

Index entries for sequences related to sigma(n)

Mathematica

odd[n_] := n/2^IntegerExponent[n, 2]; Select[Range[1, 150, 2], odd[DivisorSigma[1, #]] < # &] (* Amiram Eldar, Nov 02 2021 *)

Prog

(PARI)
A000265(n) = (n >> valuation(n, 2));
isA348741(n) = ((n%2)&&A000265(sigma(n))<n);

Crossrefs

Setwise difference A088828 \ A348743.

A088828 \ A000290 (or A088828 \ A016754) is a subsequence.

Cf. A161942, A348742.

Cf. also A348738, A348753, A348931.

Sequence in context: A320056 A175679 A088828 * A348748 A182318 A247424

Adjacent sequences: A348738 A348739 A348740 * A348742 A348743 A348744

Keyword

nonn

Author

Antti Karttunen, Nov 02 2021

Status

approved