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A098534
Mod 3 analog of Stern's diatomic series.
1
0, 1, 1, 2, 3, 2, 2, 4, 3, 4, 7, 5, 6, 5, 5, 4, 6, 4, 4, 8, 6, 8, 8, 7, 6, 10, 7, 8, 15, 11, 14, 10, 12, 10, 13, 11, 12, 11, 11, 10, 12, 10, 10, 11, 9, 8, 14, 10, 12, 10, 10, 8, 12, 8, 8, 16, 12, 16, 13, 14, 12, 17, 14, 16, 18, 16, 16, 17, 15, 14, 17, 13, 12, 22, 16, 20, 18, 17, 14, 22
OFFSET
0,4
COMMENTS
Essentially diagonal sums of Pascal's triangle modulo 3.
LINKS
FORMULA
a(n) = Sum_{k=0..floor((n-1)/2)} mod(binomial(n-k-1, k), 3).
MATHEMATICA
Table[Sum[Mod[Binomial[n - k - 1, k], 3], {k, 0, Floor[(n - 1)/2]}], {n, 0, 100}] (* G. C. Greubel, Jan 17 2018 *)
PROG
(PARI) for(n=0, 100, print1(sum(k=0, floor((n-1)/2), lift(Mod(binomial(n-k-1, k), 3))), ", ")) \\ G. C. Greubel, Jan 17 2018
(Magma) [0] cat [(&+[Binomial(n-k-1, k) mod 3: k in [0..Floor((n-1)/2)]]): n in [1..100]]; // G. C. Greubel, Jan 17 2018
CROSSREFS
Sequence in context: A131340 A337121 A175470 * A317638 A002307 A287707
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Sep 13 2004
STATUS
approved