Numbers k such that 20*R_k + 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A056656
Numbers k such that 20*R_k + 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =1a(2) =2a(3) =7a(4) =10a(5) =35a(6) =94a(7) =100a(8) =127a(9) =259a(10) =350a(11) =466a(12) =644a(13) =1010a(14) =1177a(15) =1216a(16) =2441a(17) =3760a(18) =3805a(19) =15616a(20) =26458a(21) =63116a(22) =88544a(23) =93496
External references
- oeis: A056656