OFFSET
0,3
LINKS
Indranil Ghosh, Table of n, a(n) for n = 0..10000
Michael Gilleland, Some Self-Similar Integer Sequences
Ilya Gutkovskiy, Extended graphical example
EXAMPLE
a(0) = 1;
a(1) = a(2*0+1) = sigma(a(0)) = sigma(1) = 1;
a(2) = a(2*1) = 2*a(1) = 2*1 = 2;
a(3) = a(2*1+1) = sigma(a(1)) = sigma(1) = 1;
a(4) = a(2*2) = 2*a(2) = 2*2 = 4;
a(5) = a(2*2+1) = sigma(a(2)) = sigma(2) = 1 + 2 = 3, etc.
MATHEMATICA
a[0] = 1; a[n_] := If[EvenQ[n], 2 a[n/2], DivisorSigma[1, a[(n - 1)/2]]]; Table[a[n], {n, 0, 90}]
PROG
(PARI) a(n) = if (n==0, 1, if (n%2==0, 2*a(n/2), sigma(a((n-1)/2)))); tabl(nn)={for (n=0, nn, print1(a(n), ", "); ); }; tabl(90) \\ Indranil Ghosh, Mar 03 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Mar 02 2017
STATUS
approved