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A079334 Numbers k such that k divides tau(k) and k+1 divides tau(k+1), where tau(k)=A000594(k) is Ramanujan's tau function; i.e., k and k+1 are in A063938. 2
1, 2, 3, 4, 5, 6, 7, 8, 9, 14, 15, 20, 24, 27, 35, 48, 49, 63, 80, 90, 91, 125, 160, 161, 224, 440, 728, 735, 2024, 2400, 2744, 4095, 4374, 12879, 13824, 20735, 30624 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
No other terms < 212000. - Robert G. Wilson v, Jan 06 2002
No other terms < 30000000. - Dana Jacobsen, Sep 06 2015
LINKS
Eric Weisstein's World of Mathematics, Tau Function.
MATHEMATICA
(* First do <<NumberTheory`Ramanujan` *) test[n_] := Mod[RamanujanTau[n], n]==0; Select[Range[33000], test[ # ]&&test[ #+1]&]
PROG
(PARI) tauvec(N) = Vec(q*eta(q + O(q^N))^24)
v=tauvec(10000); for(n=1, #v-1, if(Mod(v[n], n) == 0 && Mod(v[n+1], n+1) == 0, print1(n", "))) \\ Dana Jacobsen, Sep 06 2015
(Perl) use ntheory ":all"; my @p = grep { !(ramanujan_tau($_) % $_) } 1..10000; for (0 .. $#p-1) { say $p[$_] if $p[$_]+1 == $p[$_+1] } # Dana Jacobsen, Sep 06 2015
CROSSREFS
Sequence in context: A334918 A354220 A125506 * A085153 A339111 A130010
KEYWORD
nonn,more
AUTHOR
Dean Hickerson, Jan 03 2003
STATUS
approved

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Last modified March 28 10:55 EDT 2024. Contains 371241 sequences. (Running on oeis4.)