login
A123927
Characteristic function of natural numbers with number of divisors equal to a Lucas number.
2
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 1
OFFSET
1,1
FORMULA
a(n) = A102460(A000005(n)). - Antti Karttunen, Nov 22 2017
MATHEMATICA
With[{nn = 103}, Table[Boole[MemberQ[#, DivisorSigma[0, n]]], {n, nn}] &@ TakeWhile[Union@ Array[LucasL, 40, 0], # <= nn &]] (* Michael De Vlieger, Nov 22 2017 *)
PROG
(PARI)
A102460(n) = { my(u1=1, u2=3, old_u1); if(n<=2, sign(n), while(n>u2, old_u1=u1; u1=u2; u2=old_u1+u2); (u2==n)); };
A123927(n) = A102460(numdiv(n)); \\ Antti Karttunen, Nov 22 2017
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Giovanni Teofilatto, Nov 22 2006
EXTENSIONS
Superfluous 0 at the beginning of data removed by Antti Karttunen, Nov 22 2017
STATUS
approved