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A353456
Numbers k such that A353627(k) is less than A353628(k).
4
81, 162, 243, 324, 405, 486, 567, 625, 648, 810, 891, 972, 1053, 1134, 1215, 1250, 1296, 1377, 1539, 1620, 1701, 1782, 1863, 1875, 1944, 2106, 2268, 2349, 2401, 2430, 2500, 2511, 2592, 2673, 2754, 2835, 2997, 3078, 3125, 3159, 3240, 3321, 3402, 3483, 3564, 3726, 3750, 3807, 3888, 4131, 4212, 4293, 4375, 4455, 4536
OFFSET
1,1
COMMENTS
Numbers in A353511 but not in A122132. Positions where A353627 and A353628 differ from each other. See discussion in A209635.
a(8) = 625 is the first term that is not a multiple of 81.
If k is present in the sequence, then 2*k and A000265(k) are present also.
PROG
(PARI)
A001001(n) = sumdivmult(n, d, sigma(d)*d); \\ From A001001
A353628(n) = (A001001(n)%2);
A353627(n) = issquarefree(n>>valuation(n, 2));
isA353456(n) = (A353627(n) != A353628(n));
(PARI) isA353456(n) = if(issquarefree(n=(n>>valuation(n, 2))), 0, my(f=factor(n)); for(k=1, #f~, if((f[k, 2]%4)>1, return(0))); (1)); \\ After Álvar Ibeas's Nov 28 2017 comment in A209635
CROSSREFS
Setwise difference A353511 \ A122132. Subsequence of A038838.
Sequence in context: A206065 A139705 A226643 * A044251 A043454 A044632
KEYWORD
nonn
AUTHOR
Antti Karttunen, May 03 2022
STATUS
approved