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 A000966 n! never ends in this many 0's. (Formerly M3808 N1557) 17
 5, 11, 17, 23, 29, 30, 36, 42, 48, 54, 60, 61, 67, 73, 79, 85, 91, 92, 98, 104, 110, 116, 122, 123, 129, 135, 141, 147, 153, 154, 155, 161, 167, 173, 179, 185, 186, 192, 198, 204, 210, 216, 217, 223, 229, 235, 241, 247, 248, 254, 260, 266, 272, 278, 279, 285 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This sequence also holds for bases 5, 15, 20, 30, 40, 60 and 120. These bases (together with 10) are the proper divisors of 5! that are divisible by 5. - Carl R. White, Jan 21 2008 The g.f. conjectured by Simon Plouffe in 1992 dissertation is not correct; the first discrepancy is a(31) = 155, his g.f. gives 160. In fact, the g.f. for this sequence is not rational; the first differences are bounded but not periodic. - Franklin T. Adams-Watters, Jul 03 2009 REFERENCES N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). David Wells, The Penguin Dictionary of Curious and Interesting Numbers (Rev. ed. 1997), p. 42 LINKS T. D. Noe, Table of n, a(n) for n = 1..1000 Gerald Hillier, Program for HP 49G calculator, MoHPC: The Museum of HP Calculators, Sep 29 2017. L. Moser, Problem 158, Math. Mag., 27 (1953), 54-55. Solution by C. W. Trigg. L. Moser and C. W. Trigg, Problem 158 (annotated and scanned copy) A. M. Oller-Marcen, J. Maria Grau, On the Base-b Expansion of the Number of Trailing Zeros of b^k!, J. Int. Seq. 14 (2011) 11.6.8 Simon Plouffe, Approximations de séries génératrices et quelques conjectures, Dissertation, Université du Québec à Montréal, 1992. Simon Plouffe, 1031 Generating Functions and Conjectures, Université du Québec à Montréal, 1992. N. J. A. Sloane, Transforms FORMULA The simplest way to obtain this sequence is by constructing a power series A(x) = Sum_{k >= 1} x^a(k) whose exponents give the terms of the sequence. Define e(n) = (5^n-1)/4, f(n) = (1-x^(e(n)-1))/(1-x^e(n-1)), t(n) = x^(e(n)-6). Now use the recurrence A = 1 and for n >= 3, A[n] = f(n)*A[n-1]+t(n); then A = limit_{n->infinity} x^5*A[n]. This follows easily from the explicit formula for A027868(n). Here is the beginning of A: x^5 + x^11 + x^17 + x^23 + x^29 + x^30 + x^36 + x^42 + x^48 + ... - N. J. A. Sloane, Feb 02 2007 Formula from C. W. Trigg (see the Moser reference): All terms can be described as follows: for k = 1, 2, 3, ..., the number 6k-1 + floor(k/5) + floor(k/5^2) + floor(k/5^3) + ... is a term together with A112765(k) preceding numbers. [corrected and simplified by Gerald Hillier and Andrey Zabolotskiy, Sep 13 2017] EXAMPLE 17 is in the sequence because on passing from 74! to 75!, the number of end zeros jumps from 16 to 18, skipping 17. More generally, we have: n, n! ----- 0, 1 1, 1 2, 2 3, 6 4, 24 5, 120 6, 720 7, 5040 8, 40320 9, 362880 10, 3628800 11, 39916800 12, 479001600 13, 6227020800 14, 87178291200 15, 1307674368000 16, 20922789888000 17, 355687428096000 18, 6402373705728000 19, 121645100408832000 20, 2432902008176640000 21, 51090942171709440000 22, 1124000727777607680000 23, 25852016738884976640000 24, 620448401733239439360000 25, 15511210043330985984000000 <- jump from 4 to 6 trailing 0's, so 5 is a term 26, 403291461126605635584000000 27, 10888869450418352160768000000 28, 304888344611713860501504000000 29, 8841761993739701954543616000000 30, 265252859812191058636308480000000 etc. MAPLE read(transforms); e:=n->(5^n-1)/4; f:=n->(1-x^(e(n)-1))/(1-x^e(n-1)); t:=n->x^(e(n)-6); A:=1; for n from 3 to 8 do A[n]:=f(n)*A[n-1]+t(n); od: POWERS(series(x^5*A, x, 5005), x, 5005); # N. J. A. Sloane, Feb 02 2007 MATHEMATICA u=Union[FoldList[Plus, 0, IntegerExponent[Range, 5]]]; Complement[Range[u[[ -1]]], u] (* T. D. Noe, Feb 02 2007 *) zOF[n_Integer?Positive]:=Module[{maxpow=0}, While[5^maxpow<=n, maxpow++]; Plus@@Table[Quotient[n, 5^i], {i, maxpow-1}]]; Attributes[ zOF] = {Listable}; nmz[n_]:=Module[{zs=zOF[Range[n]]}, Complement[ Range[ Max[zs]], zs]]; nmz (* Harvey P. Dale, Mar 05 2017 *) PROG (PARI) valp(n, p)=my(s); while(n\=p, s+=n); s is(n)=my(t=(4*n-1)\5*5+5, s=valp(t, 5)-n); while(s<0, s+=valuation(t+=5, 5)); s>0 \\ Charles R Greathouse IV, Sep 22 2016 CROSSREFS Cf. A000142, A027868, A080066 (first differences), A191610 (complement), A096346 (same for base 3), A055938 (same for base 2), A136767-A136774. Sequence in context: A111863 A043389 A277571 * A031480 A070753 A038939 Adjacent sequences:  A000963 A000964 A000965 * A000967 A000968 A000969 KEYWORD nonn,base,nice AUTHOR EXTENSIONS More terms from Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 24 2003 Corrected by Sascha Kurz, Jan 27 2003 STATUS approved

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Last modified October 18 03:16 EDT 2019. Contains 328135 sequences. (Running on oeis4.)