1,8

a(1)=0 then a(n)=w(n)-a(n-w(n)) where w(n)=7^floor(log(n-1)/log(7))

a(n) = sum(i=1, n-1, (-1)^(i-1)*7^valuation(i, 7))

(PARI) a(n)=if(n<2, 0, 7^floor(log(n-1)/log(7))-a(n-7^floor(log(n-1)/log(7))))

(PARI) a(n)=-sum(i=1, n-1, (-1)^i*7^valuation(i, 7))

Cf. A093347, A093348

Adjacent sequences: A093346 A093347 A093348 this_sequence A093350 A093351 A093352

Sequence in context: A073084 A011473 A021570 this_sequence A020789 A093813 A092902

nonn

Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 26 2004