A182142 - OEIS

A182142

Abundance d = sigma(N) - 2*N = A033880(N) of numbers N = A153501(n), i.e., N has d > 0 as divisor.

4, 3, 2, 12, 10, 8, 4, 2, 120, 7, 56, 78, 8, 2, 2, 672, 32, 16, 4, 2, 532, 152, 136, 8, 68, 31, 992, 128, 8, 64, 32, 16, 4, 8, 128, 32, 8, 2, 43648, 2528, 32, 4, 2, 523776, 32, 2272, 32, 32, 127, 16256, 32, 32, 4, 536, 8, 32, 8, 52, 16, 32, 41044, 64

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OFFSET

1,1

COMMENTS

It is conjectured that only powers of 2 can occur more than once.

Thanks to Amiram Eldar, reference to A181595 in the definition has been corrected to A153501 (which does include triperfect numbers, as required here, in contrast to A181595 where these are excluded). - M. F. Hasler, Sep 11 2019

LINKS

M. F. Hasler, Table of n, a(n) for n = 1..200, Sep 11 2019

FORMULA

Equals A033880 o A153501.

PROG

(PARI) f182142(n)={my(d=sigma(n)-2*n); d>0 && !(n%d) && return(d)} /* Note: This is A033880(n)*is_A153501(n), neither A182142 nor is_A182142. */

for(n=1, 1e6, (t=f182142(n))&&print1(t", "))

CROSSREFS

Cf. A033880, A153501, A181595.

Sequence in context: A033882 A062111 A181596 * A033881 A099406 A274601

Adjacent sequences: A182139 A182140 A182141 * A182143 A182144 A182145

KEYWORD

nonn

AUTHOR

M. F. Hasler, Apr 14 2012

STATUS

approved