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 A063938 Numbers k that divide tau(k), where tau(k)=A000594(k) is Ramanujan's tau function. 17
 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 24, 25, 27, 28, 30, 32, 35, 36, 40, 42, 45, 48, 49, 50, 54, 56, 60, 63, 64, 70, 72, 75, 80, 81, 84, 88, 90, 91, 92, 96, 98, 100, 105, 108, 112, 115, 120, 125, 126, 128, 135, 140, 144, 147, 150, 160, 161, 162, 168 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Although most small numbers are in the sequence, it becomes sparser for larger values; e.g., only 504 numbers up to 10000 and only 184 numbers from 10001 to 20000 are in the sequence. LINKS Seiichi Manyama, Table of n, a(n) for n = 1..10000 Eric Weisstein's World of Mathematics, Tau Function. MATHEMATICA (* First do <= startvalue return filter(lambda n: not -840*(pow(m:=n+1>>1, 2, n)*(0 if n&1 else pow(m*divisor_sigma(m), 2, n))+(sum(pow(i, 4, n)*divisor_sigma(i)*divisor_sigma(n-i) for i in range(1, m))<<1)) % n, count(max(startvalue, 1))) A063938_list = list(islice(A063938_gen(), 25)) # Chai Wah Wu, Nov 08 2022 CROSSREFS For the sequence when n is prime see A007659. Cf. A063940, A000594, A079334, A296991, A296993. Sequence in context: A225737 A357315 A079333 * A002473 A174995 A161466 Adjacent sequences: A063935 A063936 A063937 * A063939 A063940 A063941 KEYWORD nonn,easy AUTHOR Robert G. Wilson v, Aug 31 2001 EXTENSIONS More terms from Dean Hickerson, Jan 03 2003 STATUS approved

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Last modified May 27 19:17 EDT 2023. Contains 362985 sequences. (Running on oeis4.)