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A065765 Sum of divisors of twice square numbers. 6
3, 15, 39, 63, 93, 195, 171, 255, 363, 465, 399, 819, 549, 855, 1209, 1023, 921, 1815, 1143, 1953, 2223, 1995, 1659, 3315, 2343, 2745, 3279, 3591, 2613, 6045, 2979, 4095, 5187, 4605, 5301, 7623, 4221, 5715, 7137, 7905, 5169, 11115, 5679, 8379, 11253 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The sum of divisors of 2m^2 [twice a square] always gives remainder r = 3 modulo 6. See A097022.

LINKS

T. D. Noe, Table of n, a(n) for n=1..10000

FORMULA

a(n)=Sigma[2*n^2]=A000203[2*A000290(n)]

a(n)=3*A065766(n)

MATHEMATICA

DivisorSigma[1, 2*Range[50]^2] (* Harvey P. Dale, Sep 06 2015 *)

PROG

(PARI) { for (n=1, 10000, write("b065765.txt", n, " ", sigma(2*n^2)) ) } [From Harry J. Smith, Oct 30 2009]

CROSSREFS

Cf. A028982, A000203, A000290

Sequence in context: A185541 A176661 A117561 * A146853 A183476 A014309

Adjacent sequences:  A065762 A065763 A065764 * A065766 A065767 A065768

KEYWORD

nonn

AUTHOR

Labos Elemer, Nov 19 2001

STATUS

approved

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Last modified June 24 08:22 EDT 2017. Contains 288697 sequences.