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A302125 Numbers whose deficiency is a perfect number. 0
7, 15, 29, 52, 62, 182, 230, 315, 344, 592, 944, 998, 1155, 2012, 2570, 4028, 6710, 15128, 19688, 20264, 30248, 36224, 38252, 40730, 43964, 52088, 90332, 96128, 168116, 195224, 258512, 262112, 451952, 538112, 991904, 1209632, 1237856, 1659128, 2080544, 2085710, 2102272, 2186132 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Subsequence of deficient numbers (A005100) whose deficiency (A033879) is a member of perfect numbers (A000396).

LINKS

Table of n, a(n) for n=1..42.

EXAMPLE

52 is in the sequence since the divisors of 52 are {1, 2, 4, 13, 26 & 52} so d(52) = 98 and 2*52 - 98 = 6, a perfect number.

MATHEMATICA

fQ[n_] := PerfectNumberQ[2n - DivisorSigma[1, n]]; Select[ Range@ 2500000, fQ]

PROG

(PARI) for(n=1, 25*10^5, d=2*n-sigma(n); d>0&&sigma(d)==2*d&&print1(n ", "))

CROSSREFS

Cf. A000396 (perfect numbers), A033879 (deficiency), A005100 (deficient numbers), A141548 (subsequence), A301859 (related sequence).

Sequence in context: A274090 A195041 A229462 * A006188 A198589 A298391

Adjacent sequences:  A302122 A302123 A302124 * A302126 A302127 A302128

KEYWORD

nonn

AUTHOR

Robert G. Wilson v and Waldemar Puszkarz, Apr 01 2018

STATUS

approved

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Last modified October 16 08:15 EDT 2019. Contains 328051 sequences. (Running on oeis4.)