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A083969 Numbers n such that 2.n.3.n.5.n.7.n.11 is prime (dot means concatenation).

%I A083969 #17 Apr 19 2021 01:07:39
%S A083969 4,18,33,42,43,57,73,76,78,87,91,93,97,102,112,114,120,141,151,177,
%T A083969 186,193,196,219,261,267,276,280,300,307,318,322,342,352,364,366,402,
%U A083969 435,438,445,457,462,468,484,511,580,582,633,646,651,679,706,745,774,783
%N A083969 Numbers n such that 2.n.3.n.5.n.7.n.11 is prime (dot means concatenation).
%H A083969 Michael S. Branicky, <a href="/A083969/b083969.txt">Table of n, a(n) for n = 1..10000</a>
%e A083969 2.4.3.4.5.4.7.4.11 = 2434547411, which is prime. Hence 4 is in the sequence.
%t A083969 v={};Do[If[PrimeQ[FromDigits[Join[{2}, IntegerDigits[n], {3}, IntegerDigits[n], {5}, IntegerDigits[n], {7}, IntegerDigits[n], {1, 1}]]], v=Append[v, n]], {n, 1000}];v
%t A083969 Select[Range[660], PrimeQ[FromDigits[Join[{2}, IntegerDigits[ # ], {3}, IntegerDigits[ # ], {5}, IntegerDigits[ # ], {7}, IntegerDigits[ # ], {1, 1}]]] &] (* _Stefan Steinerberger_, Jun 28 2007 *)
%o A083969 (Python)
%o A083969 from sympy import isprime
%o A083969 def aupton(terms):
%o A083969   n, alst = 1, []
%o A083969   while len(alst) < terms:
%o A083969     s = str(n)
%o A083969     t = int('2'+s+'3'+s+'5'+s+'7'+s+'11')
%o A083969     if isprime(t): alst.append(n)
%o A083969     n += 1
%o A083969   return alst
%o A083969 print(aupton(55)) # _Michael S. Branicky_, Apr 18 2021
%Y A083969 Cf. A083677, A032711, A092115, A092117.
%K A083969 base,easy,nonn
%O A083969 1,1
%A A083969 _Farideh Firoozbakht_, Jun 19 2003
%E A083969 Edited by _Stefan Steinerberger_, Jun 28 2007
%E A083969 Edited by _N. J. A. Sloane_, Sep 18 2008 at the suggestion of _R. J. Mathar_