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A166162 Twin prime averages which are also the sum of the divisors of a triangular number. 0
4, 12, 18, 72, 192, 270, 1488, 1872, 1482, 1872, 1152, 2268, 6552, 3672, 6552, 10890, 3528, 5280, 7560, 7488, 13680, 23040, 17388, 29760, 21600, 23040, 65520, 87120, 51480, 34848, 65268, 127680, 122400, 134400, 114660, 137088, 206640, 134400 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..38.

EXAMPLE

The triangular number A000217(3)= 6 has a sum of divisors 1+2+3+6 = 12 = A014574(3) which is also the average of the twin primes 11 and 13.

MATHEMATICA

t[n_]:=n*(n+1)/2; f[n_]:=Plus@@Divisors[t[n]]; lst={}; Do[p=f[n]; If[PrimeQ[p-1]&&PrimeQ[p+1], AppendTo[lst, p]], {n, 7!}]; lst

CROSSREFS

Cf. A074285, A014574 [R. J. Mathar, Oct 14 2008]

Sequence in context: A307623 A307624 A177833 * A228166 A244433 A086109

Adjacent sequences:  A166159 A166160 A166161 * A166163 A166164 A166165

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Oct 08 2009

EXTENSIONS

Definition and example rewritten by R. J. Mathar, Oct 14 2009

STATUS

approved

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Last modified October 18 03:25 EDT 2021. Contains 348065 sequences. (Running on oeis4.)