OFFSET
1,2
COMMENTS
Conjecture: all odd numbers not of the type 10k+5 are members.
Some of the larger entries may only correspond to probable primes.
Values corresponding to a(6)=27 (A083755(5)) through a(59)=363 (A083755(58), a 149-digit value) have been certified prime with Primo. - Rick L. Shepherd, May 10 2003
Since we begin with 1 and thereafter have more than a single decimal digit, all terms must be in A045572, the sequence that contains all positive integers relatively prime to 10. - Michael De Vlieger, Oct 30 2020.
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..501
Michael De Vlieger, Plot of a(n) for 1 <= n <= 500, showing congruency of a(n) with 1 (orange), 3 (green), 7 (blue), or 9 (magenta) (mod 10).
EXAMPLE
13,137,13711, etc. are primes.(1379 is not a prime) hence 11 is the next member after 7.
MATHEMATICA
Block[{c = 1, a = {1}, f, g}, f[m_, n_] := m*10^(1 + Floor[Log10[n]]) + n; g[n_] := (5 n + Mod[3 n + 2, 4] - 4)/2; Do[Block[{j = 2, k, d, t}, While[Nand[FreeQ[a, Set[k, g[j] ]], PrimeQ[Set[d, f[c, k]]]], j++]; c = d; AppendTo[a, k]], {i, 59}]; a] (* Michael De Vlieger, Oct 30 2020 *)
PROG
(PARI) {used_before(v, n) = for (l=1, matsize(v)[2], if(v[l]==n, return(1))); return(0)} {A083754=[1]; p=A083754[1]; A083755=[]; print1(A083754[1], ", "); for (m=2, 151, k=1; while (used_before(A083754, k)||!isprime(tmp_p=p*(10^length(Str(k)))+k), k=k+2); p=tmp_p; A083755=concat(A083755, p); A083754=concat(A083754, k); print1(A083754[m], ", ")); A083755}
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), May 06 2003
EXTENSIONS
More terms from Rick L. Shepherd, May 08 2003
STATUS
approved