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 A113588 a(1) = 3, a(n+1) = d!, where d is the sum of decimal digits of a(n). 2
 3, 6, 720, 362880, 10888869450418352160768000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The next term, a(6) = 108!, has 175 digits. - If one omits to take the sum of the digits, i.e., a(n+1)=a(n)!, where a(1)=3 is the least starting value that does not lead to a constant sequence, then the first three terms are the same but a(4) has 1747 digits. - M. F. Hasler, Mar 15 2016 LINKS Table of n, a(n) for n=1..5. FORMULA a(n+1) = A000142(A007953(a(n))). - M. F. Hasler, Mar 15 2016 EXAMPLE a(2) = 6; a(3) = 6! = 720; a(4) = (7+2+0)! = 9! = 362880; a(5) = 27!. MAPLE A007953 := proc(n) add(i, i= convert(n, base, 10)) ; end: A113588 := proc(n) option remember ; if n = 1 then 3; else factorial(A007953(A113588(n-1)) ) ; fi; end: for n from 1 to 6 do printf("%d, ", A113588(n)) ; od: # R. J. Mathar, Feb 06 2008 MATHEMATICA NestList[Factorial@ Total[IntegerDigits@ #] &, 3, 4] (* Michael De Vlieger, Mar 15 2016 *) PROG (PARI) A007953(n, a=3)={for(i=2, n, a=sumdigits(a)!); a} \\ M. F. Hasler, Mar 15 2016 CROSSREFS Sequence in context: A171928 A308259 A034879 * A071106 A157548 A134901 Adjacent sequences: A113585 A113586 A113587 * A113589 A113590 A113591 KEYWORD nonn,base AUTHOR Amarnath Murthy, Nov 07 2005 EXTENSIONS More terms from R. J. Mathar, Feb 06 2008 STATUS approved

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Last modified May 20 13:56 EDT 2024. Contains 372716 sequences. (Running on oeis4.)