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A079394 Compare t(n) and t(n+1) where t = Ramanujan's tau function (A000594); a(n) = pq where p and q are given below. 0
21, 31, 21, 31, 21, 11, 31, 21, 11, 31, 22, 11, 32, 41, 42, 21, 32, 41, 22, 12, 11, 31, 41, 21, 32, 21, 32, 41, 22, 11, 11, 32, 41, 22, 31, 21, 11, 12, 31, 42, 42, 22, 11, 12, 12, 31, 42, 21, 32, 21, 32, 21, 31, 41, 22, 31, 21, 11, 12, 31, 42, 41, 41, 21, 11, 11, 32, 42, 42 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

p = 1 if t(n) < 0, t(n+1) < 0; p = 2 if t(n) >= 0, t(n+1) < 0; p = 3 if t(n) < 0, t(n+1) >= 0; p = 4 if t(n) >= 0, t(n+1) >= 0.

q = 1 if |t(n)| <= t(n+1); q = 2 if |t(n)| > t(n+1.

LINKS

Table of n, a(n) for n=0..68.

EXAMPLE

A000594(1)=1, A000594(2)=-24. Hence the sign changes from + to - and the modulus increasing. Consulting the key, this gives a(1)=21.

PROG

(PARI) T(n)=n*(n+1)/2 rtau3(n)=local(y, j); y=0; j=1; while (T(j-1)<n, j++); j--; for (i=1, j, y=y-(-1)^i*(2*i-1)*x^(T(i-1))); y=y^8; polcoeff(y, n-1) for (n=1, 100, r3=rtau3(n); r31=rtau3(n+1); rn=(sign(r3)+1)/2; rn1=sign(r31)+1; print1((rn+rn1+1)""(abs(r3)>abs(r31))+1", "))

CROSSREFS

Cf. A000594.

Sequence in context: A115433 A116096 A116116 * A112375 A067599 A261322

Adjacent sequences:  A079391 A079392 A079393 * A079395 A079396 A079397

KEYWORD

nonn

AUTHOR

Jon Perry, Jan 06 2003

STATUS

approved

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Last modified November 12 19:41 EST 2019. Contains 329078 sequences. (Running on oeis4.)