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A091290
Numbers n such that sigma(n) + sigma(n+1) <= sigma(2*n+1).
6
1, 4, 7, 10, 13, 22, 31, 37, 46, 49, 52, 58, 61, 67, 73, 82, 85, 94, 97, 106, 112, 115, 121, 127, 130, 136, 142, 148, 157, 166, 172, 178, 181, 187, 193, 202, 211, 214, 217, 226, 229, 232, 238, 241, 247, 253, 256, 262, 274, 277, 283, 292, 298, 301, 307, 310, 313
OFFSET
1,2
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
MATHEMATICA
Do[s=(DivisorSigma[1, n]+DivisorSigma[1, n+1])/ DivisorSigma[1, 2*n+1]; If[ !Greater[s, 1], Print[n]], {n, 1, 10000000}]
PROG
(PARI) is(n)=sigma(n)+sigma(n+1)<=sigma(2*n+1) \\ Charles R Greathouse IV, Feb 14 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Feb 16 2004
EXTENSIONS
New name from Charles R Greathouse IV, Feb 14 2013
STATUS
approved