

A114705


Sum of divisors of 2^n + 3^n.


1



6, 14, 48, 98, 372, 868, 2784, 7236, 27744, 64708, 215040, 541156, 1947840, 5168548, 23046144, 43129476, 155189760, 444228512, 1398675600, 3623742864, 14636428992, 33799504228, 113272236000, 299806597512, 1154553386688
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OFFSET

1,1


COMMENTS

The terms are never squares. For n>=2, 2^n+3^n falls into a pattern of quadratic nonresidues, taken modulo 20: 13, 15, 17, 15, 13, 15, 17, 15, ...  Jack Brennen, Dec 25 2005
a(n) is always even because 2^n+3^n is never a quadratic residue modulo 15.  Jose Brox (tautocrona(AT)terra.es), Dec 27 2005


LINKS

Table of n, a(n) for n=1..25.


EXAMPLE

a(3)=48 because 2^3+3^3=8+27=35 has divisors 1,5,7,35 sum of which is 48.


MATHEMATICA

Table[DivisorSigma[1, 2^n+3^n], {n, 1, 30}]


CROSSREFS

Cf. A000203.
Sequence in context: A093369 A130443 A005515 * A200187 A107301 A118432
Adjacent sequences: A114702 A114703 A114704 * A114706 A114707 A114708


KEYWORD

nonn


AUTHOR

Zak Seidov, Dec 26 2005


STATUS

approved



