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A079334 Numbers n such that n divides tau(n) and n+1 divides tau(n+1), where tau(n)=A000594(n) is Ramanujan's tau function; i.e., n and n+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

Table of n, a(n) for n=1..37.

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

Cf. A000594, A063938.

Sequence in context: A174876 A092597 A125506 * A085153 A130010 A282765

Adjacent sequences:  A079331 A079332 A079333 * A079335 A079336 A079337

KEYWORD

nonn,more

AUTHOR

Dean Hickerson, Jan 03 2003

STATUS

approved

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Last modified February 19 19:21 EST 2020. Contains 332047 sequences. (Running on oeis4.)