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A373283
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Expansion of Sum_{k>=0} x^(7^k) / (1 - 7*x^(7^k)).
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5
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1, 7, 49, 343, 2401, 16807, 117650, 823543, 5764801, 40353607, 282475249, 1977326743, 13841287201, 96889010414, 678223072849, 4747561509943, 33232930569601, 232630513987207, 1628413597910449, 11398895185373143, 79792266297612050, 558545864083284007
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OFFSET
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1,2
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LINKS
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FORMULA
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G.f. A(x) satisfies A(x) = x/(1 - 7*x) + A(x^7).
If n == 0 (mod 7), a(n) = 7^n + a(n/7) otherwise a(n) = 7^n.
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PROG
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(PARI) b(n, k) = sumdiv(n, d, (gcd(d, k)==1)*(moebius(d)*k^(n/d)))/(k*n);
a(n, k=7) = sumdiv(n, d, d*b(d, k));
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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