A276694 Where records occur in A209252.

0, 11, 13, 101, 107, 177, 357, 1001, 1011, 10759, 11487, 42189, 113183, 344253, 1851759, 4787769, 15848679, 139367847, 240889077, 1167555543, 111738007953

Offset: 1

Author

Paolo P. Lava, Sep 14 2016

Keywords

• nonn
• base
• more

Comments

Except for the first term, all terms are coprime to 10. - Chai Wah Wu, Sep 19 2016

Crossrefs

Cf. A000040, A209252.

Programs

Maple

with(numtheory): P:= proc(q) local d,j,k,n,t,x; x:=4; print(0);
for n from 1 to q do d:=ilog10(n)+1; t:=0;
for k from 0 to d-1 do for j from 0 to 9 do
if isprime(trunc(n/10^(k+1))*10^(k+1)+j*10^k+(n mod 10^k))
then t:=t+1; fi; od; od;
if isprime(n) then if t-d>x then x:=t-d; print(n); fi; else
if t>x then x:=t; print(n); fi; fi; od; end: P(10^9);

Extensions

a(18)-a(19) from Chai Wah Wu, Sep 19 2016

a(20) from Michael S. Branicky, Apr 21 2025

a(21) from Michael S. Branicky, May 21 2025