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 A343498 a(n) = Sum_{k=1..n} gcd(k, n)^4. 7
 1, 17, 83, 274, 629, 1411, 2407, 4388, 6729, 10693, 14651, 22742, 28573, 40919, 52207, 70216, 83537, 114393, 130339, 172346, 199781, 249067, 279863, 364204, 393145, 485741, 545067, 659518, 707309, 887519, 923551, 1123472, 1216033, 1420129, 1514003, 1843746, 1874197 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Seiichi Manyama, Table of n, a(n) for n = 1..10000 FORMULA a(n) = Sum_{d|n} phi(n/d) * d^4. a(n) = Sum_{d|n} mu(n/d) * d * sigma_3(d). G.f.: Sum_{k >= 1} phi(k) * x^k * (1 + 11*x^k + 11*x^(2*k) + x^(3*k))/(1 - x^k)^5. Dirichlet g.f.: zeta(s-1) * zeta(s-4) / zeta(s). - Ilya Gutkovskiy, Apr 18 2021 Sum_{k=1..n} a(k) ~ Pi^4 * n^5 / (450*zeta(5)). - Vaclav Kotesovec, May 20 2021 MATHEMATICA a[n_] := Sum[GCD[k, n]^4, {k, 1, n}]; Array[a, 50] (* Amiram Eldar, Apr 18 2021 *) PROG (PARI) a(n) = sum(k=1, n, gcd(k, n)^4); (PARI) a(n) = sumdiv(n, d, eulerphi(n/d)*d^4); (PARI) a(n) = sumdiv(n, d, moebius(n/d)*d*sigma(d, 3)); (PARI) my(N=40, x='x+O('x^N)); Vec(sum(k=1, N, eulerphi(k)*x^k*(1+11*x^k+11*x^(2*k)+x^(3*k))/(1-x^k)^5)) CROSSREFS Column 4 of A343510. Cf. A000010, A001158 (sigma_3(n)), A018804, A054611, A069097, A332517, A342423, A342433, A343497, A343499, A343514. Sequence in context: A296401 A259142 A142059 * A318743 A193046 A158528 Adjacent sequences:  A343495 A343496 A343497 * A343499 A343500 A343501 KEYWORD nonn,mult AUTHOR Seiichi Manyama, Apr 17 2021 STATUS approved

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Last modified August 3 22:03 EDT 2021. Contains 346441 sequences. (Running on oeis4.)