OFFSET

0,2

COMMENTS

a(n) is the least k such that there are exactly n distinct primes of the form A007504(k) mod p for the first k primes p.

LINKS

Robert Israel, Table of n, a(n) for n = 0..1000

EXAMPLE

a(4) = 25 because A007504(25) = 1060 and there are 4 primes of the form 1060 mod p for the first 25 primes p: 2 = 1060 mod 23, 3 = 1060 mod 7, 7 = 1060 mod 13 and 23 = 1060 mod 61, and 25 is the first k that produces exactly 4 primes in this way.

MAPLE

N:= 100: # for a(0)..a(N)

V:= Array(0..N): count:= 0:

P:= {}: p:= 1: t:= 0:

for n from 1 while count < 100 do

p:= nextprime(p); P:= P union {p}; t:= t+p;

v:= nops(select(isprime, map(s -> t mod s, P)));

if v <= N and V[v] = 0 then

V[v]:= n; count:= count+1;

fi

od:

convert(V, list);

CROSSREFS

KEYWORD

nonn

AUTHOR

J. M. Bergot and Robert Israel, Apr 29 2021

STATUS

approved