This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A069604 #7 Jun 22 2025 07:16:52
%S A069604 1,1,3,11,1,3,3,53,13,39,9,3,399,11,9,133,3,11,51,111,13,53,31,3,173,
%T A069604 1,317,519,579,1,573,357,5111,39,51,73,3317,1977,5173,579,357,359,9,
%U A069604 57,3991,959,951,7,111,1959,39,191,3357,3151,3137,577,117,1353,951,153,99
%N A069604 a(1) = 1; for n>1, a(n) = smallest number with all odd digits giving a prime in concatenation with the previous terms.
%e A069604 a(5) = 1 and the number 113111 is a prime.
%t A069604 a[1] = 1; a[n_] := a[n] = Block[{k = 1, c = IntegerDigits @ Table[ a[i], {i, n - 1}]}, While[ Union[ Mod[ IntegerDigits[k], 2]] != {1} || !PrimeQ[ FromDigits[ Join[ Flatten[c], IntegerDigits[k]]]], k = k + 1]; k]; Table[ a[n], {n, 61}] (* corrected by _Jason Yuen_, Jun 22 2025 *)
%Y A069604 Cf. A033680, A074336, A092528, A069602.
%K A069604 nonn,base
%O A069604 1,3
%A A069604 _Amarnath Murthy_, Mar 26 2002
%E A069604 Corrected and extended by Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 30 2003