A038526 Concatenation of prime factors of n-th Fibonacci number.

2, 3, 5, 222, 13, 37, 217, 511, 89, 222233, 233, 1329, 2561, 3747, 1597, 2221719, 37113, 351141, 213421, 89199, 28657, 2222233723, 553001, 233521, 21753109, 31329281, 514229, 2225113161, 5572417, 37472207, 28919801, 15973571, 513141961, 22223331719107, 731492221

Offset: 3

Author

Jeff Burch

Keywords

• nonn
• base

Links

• Alois P. Heinz, Table of n, a(n) for n = 3..380

Programs

Maple

A055642 := proc(n) if n =0 then 1 ; else ilog10(n)+1 ; fi ; end: catDigs := proc(L) local a,k,i ; a := 0 ; for i from 1 to nops(L) do a := a*10^A055642(L[i])+L[i] ; od ; end: A037276 := proc(n) local L,i,ifs,j ; if n = 1 then 0 else ifs := ifactors(n)[2] ; L := [] ; for i in ifs do for j from 1 to op(2,i) do L := [op(L),op(1,i)] ; od: od: catDigs(L) ; fi ; end: A038526 := proc(n) A037276(combinat[fibonacci](n)) ; end: seq(A038526(n),n=3..20) ; # R. J. Mathar, Oct 12 2007
# second Maple program:
F:= n-> (<<0|1>, <1|1>>^n)[1, 2]:
a:= n-> parse(cat(sort(map(i-> i[1]$i[2], ifactors(F(n))[2]))[])):
seq(a(n), n=3..40);  # Alois P. Heinz, Aug 17 2018

Formula

a(n) = A037276(A000045(n)). - R. J. Mathar, Oct 12 2007

Extensions

Edited by Charles R Greathouse IV, Apr 27 2010