A357238 Inverse Moebius transform of tribonacci numbers (A000073).
0, 1, 1, 3, 4, 9, 13, 27, 45, 86, 149, 285, 504, 941, 1710, 3163, 5768, 10662, 19513, 35978, 66026, 121565, 223317, 411053, 755480, 1390042, 2555802, 4701713, 8646064, 15904390, 29249425, 53801243, 98950246, 182003370, 334745794, 615704412, 1132436852, 2082895617, 3831006934
Offset: 1
Keywords
Programs
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Mathematica
nmax = 39; CoefficientList[Series[Sum[x^(2 k)/(1 - x^k - x^(2 k) - x^(3 k)), {k, 1, nmax}], {x, 0, nmax}], x] // Rest -
PARI
f(n) = ([0, 1, 0; 0, 0, 1; 1, 1, 1]^n)[1, 3]; \\ A000073 a(n) = sumdiv(n, d, f(d)); \\ Michel Marcus, Sep 20 2022