

A156942


Odd abundant numbers whose abundance is odd.


4



11025, 99225, 245025, 275625, 342225, 540225, 893025, 1334025, 1863225, 2205225, 2480625, 3080025, 3186225, 3980025, 4601025, 4862025, 5832225, 6125625, 6890625, 7868025, 8037225, 8555625, 9272025, 9828225, 10595025, 10989225
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OFFSET

1,1


COMMENTS

Number of terms <10^n: 0, 0, 0, 0, 2, 7, 24, 83, 250, 792, 2484, 7988, 25383, 80082, ..., . Not all are a multiple of 25, i.e.; 81162081 = 9009^2 = (9*7*11*13)^2. See A156943.
n must be an odd square. Square roots are in A174830.


LINKS

R. G. Wilson v, Table of n, a(n) for n = 1..1000


MATHEMATICA

fQ[n_] := Block[{ds = DivisorSigma[1, n]  2 n}, ds > 0 && OddQ@ ds]; Select[ Range[1, 12006223, 2], fQ @# &]


PROG

(PARI) is(n)=my(s=sigma(n)); n%2 && s>2*n && (s2*n)%2 \\ Charles R Greathouse IV, Feb 21 2017


CROSSREFS

Cf. A156903, A156943, A174830.
Sequence in context: A160711 A129087 A239828 * A164518 A198208 A139409
Adjacent sequences: A156939 A156940 A156941 * A156943 A156944 A156945


KEYWORD

nonn


AUTHOR

Robert G. Wilson v, Feb 18 2009


EXTENSIONS

Edited by Robert G. Wilson v at the suggestion of T. D. Noe, Mar 30 2010


STATUS

approved



