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A191599
Numbers k that do not divide Ramanujan's tau(k).
2
11, 13, 17, 19, 22, 23, 26, 29, 31, 33, 34, 37, 38, 39, 41, 43, 44, 46, 47, 51, 52, 53, 55, 57, 58, 59, 61, 62, 65, 66, 67, 68, 69, 71, 73, 74, 76, 77, 78, 79, 82, 83, 85, 86, 87, 89, 93, 94, 95, 97, 99, 101, 102, 103, 104, 106, 107, 109, 110, 111, 113, 114
OFFSET
1,1
COMMENTS
This sequence has its first 45 terms in common with A068191.
Subsequence of A068191.
Complement of A063938. - Omar E. Pol, Aug 28 2011
LINKS
B. Ramakrishnan and Brundaban Sahu, Rankin-Cohen brackets and Van der Pol-type identities for the Ramanujan's tau function, arXiv:0711.3512 [math.NT], 2007, pp. 14. See Corollary 2.11
EXAMPLE
For n=1, a(1)=11 since 11 does not divide tau(11) = 534612.
MAPLE
with(numtheory): tn := proc(n) modp(-840*sum(k^4*sigma(k)*sigma(n-k), k=1..n-1), n); end; ser := proc(a, b) local n, lis; lis := []; for n from a to b do if tn(n) <> 0 then lis := [op(lis), n]; fi; od; lis; end;
MATHEMATICA
Select[Range[120], !Divisible[RamanujanTau[#], #]&] (* Jean-François Alcover, Nov 29 2017 *)
PROG
(PARI) isok(k) = ramanujantau(k) % k; \\ Michel Marcus, Aug 14 2021
CROSSREFS
Sequence in context: A333237 A048388 A068191 * A084374 A063193 A056758
KEYWORD
nonn
AUTHOR
Luis H. Gallardo, Jun 08 2011
STATUS
approved