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A137992

A014137 (= partial sums of Catalan numbers A000108) mod 3.

1, 2, 1, 0, 2, 2, 2, 2, 1, 0, 2, 0, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 0, 2, 0, 1, 2, 2, 2, 2, 0, 1, 2, 1, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2

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OFFSET

0,2

COMMENTS

As usual, "mod 3" means to choose the unique representative in { 0,1,2 } of the equivalence class modulo 3Z.

LINKS

Table of n, a(n) for n=0..79.

FORMULA

a(n) = sum( k=0..n, C(k) ) (mod 3), where C(k) = binomial(2k,k)/(k+1).

a(n) = 1 <=> n = 2 A137821(m) for some m (with A137821(0)=0).

PROG

(PARI) A137992(n) = lift( sum( k=0, n, binomial( 2*k, k )/(k+1), Mod(0, 3) ))

CROSSREFS

Cf. A014137, A000108, A137821-A137824, A107755; A014138(n)+1 = a(n+1) (mod 3).

Sequence in context: A307332 A275409 A029343 * A047654 A358477 A351981

Adjacent sequences: A137989 A137990 A137991 * A137993 A137994 A137995

KEYWORD

easy,nonn

AUTHOR

M. F. Hasler, Mar 16 2008

STATUS

approved

URL: https://oeis.org/A137992

⇱ A137992 - OEIS