A270475 Integers n such that A003266(n) is not divisible by n*(n+1)/2.

2, 3, 4, 6, 7, 22, 23, 42, 43, 66, 67, 82, 83, 102, 103, 126, 127, 162, 163, 166, 167, 222, 223, 226, 227, 282, 283, 366, 367, 382, 383, 442, 443, 462, 463, 466, 467, 486, 487, 502, 503, 522, 523, 546, 547, 586, 587, 606, 607, 642, 643, 646, 647, 682, 683, 726, 727, 786, 787

Offset: 1

Author

Altug Alkan, Mar 17 2016

Keywords

• nonn

Comments

This sequence contains primes dividing all Fibonacci sequences.

Examples

			6 is a term because (1*1*2*3*5*8) is not divisible by (1+2+3+4+5+6).
5 is not a term because (1*1*2*3*5) is divisible by (1+2+3+4+5).
		

Crossrefs

Cf. A000040, A000057, A003266.

Programs

Mathematica

nn = 800; Function[k, Select[Range@ nn, ! Divisible[k[[#]], # (# + 1)/2] &]]@ FoldList[Times, Array[Fibonacci@ # &, nn]] (* Michael De Vlieger, Mar 19 2016 *)

PARI

a(n) = prod(k=1, n, fibonacci(k));
for(n=1, 1e3, if(a(n) % (n*(n+1)/2) != 0, print1(n, ", ")));