A102137 - OEIS

%I #19 Nov 09 2018 22:12:39

%S 4,6,7,19,43,48,109,122,628,1689,6208,6309,15479,21651

%N Iccanobirt prime indices (7 of 15): Indices of prime numbers in A102117.

%C a(15) > 50000. - _Robert Price_, Nov 09 2018

%F A102117(a(n)) = A102157(n).

%p rev:= proc(n) local i, L;

%p L:= convert(n,base, 10);

%p add(L[-i]*10^(i-1),i=1..nops(L))

%p end proc:

%p A[0]:= 0: A[1]:= 0: A[2]:= 1:

%p RA[0]:=0: RA[1]:= 0: RA[2]:= 1:

%p count:= 0:

%p for n from 3 to 10000 do

%p   A[n]:= RA[n-1]+RA[n-2]+RA[n-3];

%p   RA[n]:= rev(A[n]);

%p   if isprime(A[n]) then count:= count+1; a[count]:= n fi

%p od:

%p seq(a[i],i=1..count); # _Robert Israel_, Aug 04 2016

%t Flatten[Position[Transpose[NestList[nxt,{0,0,1},1700]][[1]],_?PrimeQ]]-1 (* _Harvey P. Dale_, Nov 28 2015 *)

%Y Cf. A000040, A102117, A102131-A102145.

%K nonn,more,base

%O 1,1

%A _Jonathan Vos Post_ and _Ray Chandler_, Dec 31 2004

%E a(11)-a(13) from _Robert Israel_, Aug 04 2016

%E a(14) from _Robert Price_, Nov 09 2018