login
A348741
Odd numbers k for which A161942(k) < k, where A161942 is the odd part of sigma.
6
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.
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. also A348738, A348753, A348931.
Sequence in context: A320056 A175679 A088828 * A348748 A182318 A376218
KEYWORD
nonn
AUTHOR
Antti Karttunen, Nov 02 2021
STATUS
approved