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A086417 Sum of divisors of 3-smooth numbers. 4
1, 3, 4, 7, 12, 15, 13, 28, 31, 39, 60, 40, 63, 91, 124, 120, 127, 195, 121, 252, 280, 255, 403, 363, 508, 600, 364, 511, 819, 847, 1020, 1240, 1092, 1023, 1651, 1815, 1093, 2044, 2520, 2548, 2047, 3315, 3751, 3279, 4092, 5080, 5460, 4095, 3280 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A000203(A003586(n));

a(n) = (2^(A022328(n)+1)-1)*(3^(A022329(n)+1)-1)/2.

a(n) = A000225(j) * A003462(k) for some j,k > 0. - Flávio V. Fernandes, May 29 2021

MATHEMATICA

DivisorSigma[1, #]&/@Select[Range[4000], Max[FactorInteger[#][[All, 1]]]<4&] (* Harvey P. Dale, Feb 14 2017 *)

PROG

(Haskell)

a086417 n = (2 ^ (a022328 n + 1) - 1) * (3 ^ (a022329 n + 1) - 1) `div` 2

-- Reinhard Zumkeller, Nov 19 2015

CROSSREFS

Cf. A086416.

Cf. A000203, A003586, A022328, A022329.

Sequence in context: A305185 A083561 A018195 * A051215 A192112 A034885

Adjacent sequences:  A086414 A086415 A086416 * A086418 A086419 A086420

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jul 18 2003

STATUS

approved

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Last modified September 19 12:44 EDT 2021. Contains 347556 sequences. (Running on oeis4.)