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 A077713 a(1) = 3; thereafter a(n) = the smallest prime of the form d0...0a(n-1), where d is a single digit, or 0 if no such prime exists. 4
 3, 13, 113, 2113, 12113, 612113, 50612113, 1050612113, 6001050612113, 26001050612113, 1026001050612113, 6000001026001050612113, 500006000001026001050612113, 600500006000001026001050612113, 1600500006000001026001050612113, 6001600500006000001026001050612113 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n) is the smallest prime obtained by prefixing a(n-1) with a number of the form d*10^k where d is a single digit, 0 < d < 10, and k >= 0. Conjecture: d*10^k always exists. LINKS Michael S. Branicky, Table of n, a(n) for n = 1..44 EXAMPLE a(7) = 50612113: deleting 5 gives 612113 = a(6). MAPLE a:= proc(n) option remember; local k, m, d, p; if n=1 then 3 else k:= a(n-1); for m from length(k) do for d to 9 do p:= k +d*10^m; if isprime(p) then return p fi od od fi end: seq(a(n), n=1..20); # Alois P. Heinz, Jan 12 2015 PROG (Python) from sympy import isprime from itertools import islice def agen(an=3): while True: yield an pow10 = 10**len(str(an)) while True: found = False for t in range(pow10+an, 10*pow10+an, pow10): if isprime(t): an = t; found = True; break if found: break pow10 *= 10 print(list(islice(agen(), 16))) # Michael S. Branicky, Jun 23 2022 CROSSREFS Cf. A053583, A077714, A077715, A077716. Sequence in context: A105431 A360187 A053583 * A119723 A093011 A262147 Adjacent sequences: A077710 A077711 A077712 * A077714 A077715 A077716 KEYWORD base,nonn AUTHOR Amarnath Murthy, Nov 19 2002 EXTENSIONS More terms from Ray Chandler, Jul 23 2003 Changed offset to 1 by Alois P. Heinz, Jan 12 2015 Definition clarified by N. J. A. Sloane, Jan 19 2015 STATUS approved

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Last modified June 3 09:36 EDT 2023. Contains 363107 sequences. (Running on oeis4.)