The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A321823 a(n) = Sum_{d|n, d==1 mod 4} d^7 - Sum_{d|n, d==3 mod 4} d^7. 3
 1, 1, -2186, 1, 78126, -2186, -823542, 1, 4780783, 78126, -19487170, -2186, 62748518, -823542, -170783436, 1, 410338674, 4780783, -893871738, 78126, 1800262812, -19487170, -3404825446, -2186, 6103593751, 62748518, -10455572420, -823542 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Seiichi Manyama, Table of n, a(n) for n = 1..10000 J. W. L. Glaisher, On the representations of a number as the sum of two, four, six, eight, ten, and twelve squares, Quart. J. Math. 38 (1907), 1-62 (see p. 4 and p. 8). FORMULA a(n) = a(A000265(n)). - M. F. Hasler, Nov 26 2018 G.f.: Sum_{k>=1} (-1)^(k-1)*(2*k - 1)^7*x^(2*k-1)/(1 - x^(2*k-1)). - Ilya Gutkovskiy, Dec 06 2018 MATHEMATICA s[n_, r_] := DivisorSum[n, #^7 &, Mod[#, 4] == r &]; a[n_] := s[n, 1] - s[n, 3]; Array[a, 30] (* Amiram Eldar, Nov 26 2018 *) PROG (PARI) apply( A321823(n)=sumdiv(n>>valuation(n, 2), d, (2-d%4)*d^7), [1..40]) \\ M. F. Hasler, Nov 26 2018 CROSSREFS Column k=7 of A322143. Cf. A321543 - A321565, A321807 - A321836 for similar sequences. Sequence in context: A059757 A068304 A152816 * A215960 A279070 A046320 Adjacent sequences:  A321820 A321821 A321822 * A321824 A321825 A321826 KEYWORD sign,mult AUTHOR N. J. A. Sloane, Nov 24 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 26 05:58 EST 2021. Contains 340432 sequences. (Running on oeis4.)