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 A254449 a(n) is the smallest nonnegative integer such that a(n)! contains a string of exactly n consecutive 4's. 11
 0, 4, 21, 63, 117, 375, 1325, 1253, 5741, 30455, 83393, 68094, 565882, 2666148, 1514639 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(6) and a(7) are anagrams. LINKS EXAMPLE a(1) = 4 since 4! = 24 contains '4', and 4 is the smallest integer for which this condition is met. a(2) = 21 since 21! = 51090942171709440000 contains '44'. MATHEMATICA A254449[n_] := Module[{m = 0},    t = Table[4, n];    While[! MemberQ[Split[IntegerDigits[m!]], t], m++]; m]; Join[{0}, Table[A254449[n], {n, 1, 14}]] (* Robert Price, Mar 20 2019 *) PROG (Python) def A254449(n):     if n == 0:         return 0     i, m, s = 1, 1, '4'*n     s2 = s+'4'     while True:         m *= i         sn = str(m)         if s in sn and s2 not in sn:             return i         i += 1 # Chai Wah Wu, Dec 29 2015 CROSSREFS Cf. A254042, A254447, A254448, A254500, A254501, A254502, A254716, A254717, A252652. Sequence in context: A242135 A332981 A135559 * A131478 A089893 A212246 Adjacent sequences:  A254446 A254447 A254448 * A254450 A254451 A254452 KEYWORD nonn,more,base AUTHOR Martin Y. Champel, Jan 30 2015 EXTENSIONS a(12) from Jon E. Schoenfield, Feb 27 2015 a(0) prepended by Jon E. Schoenfield, Mar 01 2015 a(14) by Lars Blomberg, Mar 19 2015 a(13) by Bert Dobbelaere, Oct 29 2018 STATUS approved

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Last modified June 23 12:08 EDT 2021. Contains 345401 sequences. (Running on oeis4.)