OFFSET
1,1
COMMENTS
Subsequence of A030430 (primes of the form 10n+1). - Michel Marcus, Dec 04 2015
If m is a term then (m-1)/10 is divisible by a cube (A000578) and the resulting quotient, different from 1, is in A076289. - Michel Marcus, Dec 05 2015
Without the "repeated at least twice" constraint, A168147 would be a subsequence. - Michel Marcus, Dec 05 2015
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
8 = 2^3; 881 is prime.
27 = 3^3; 27271 is prime.
MAPLE
N:= 20: # to get all terms with at most N digits
M:= floor((N-1)/2):
res:= {}:
for s from 1 to floor(10^(M/3)) do
x:= s^3;
m:= 1+ilog10(x);
for k from 2 to floor((N-1)/m) do
p:= x*add(10^(1+m*i), i=0..k-1)+1;
if isprime(p) then res:= res union {p} fi;
od
od:
sort(convert(res, list)); # Robert Israel, Jan 13 2016
MATHEMATICA
Take[Sort@ Flatten[Select[#, PrimeQ] & /@ Table[FromDigits@ Append[Flatten@ IntegerDigits@ Table[n^3, {#}], 1] & /@ Range[2, 20], {n, 1, 300}] /. {} -> Nothing], 27] (* Michael De Vlieger, Jan 05 2016 *)
PROG
(Python)
from itertools import count, islice
from sympy import isprime
def A265181_gen(): # generator of terms
return filter(isprime, (int(str(k**3)*2)*10+1 for k in count(1)))
KEYWORD
nonn,base
AUTHOR
Thomas S. Pedigo, Dec 03 2015
STATUS
approved