Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 4500 articles have referenced us, often saying "we would not have discovered this result without the OEIS".
Table of n, a(n) for n=1..62.
(PARI) a(n)=sum(k=1, n, -sum(i=1, k-1, (-1)^i*7^valuation(i, 7)))
Sequence in context: A195952 A236545 A095060 * A097365 A156906 A216245
Adjacent sequences: A094114 A094115 A094116 * A094118 A094119 A094120
Benoit Cloitre, May 03 2004