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A031972 a(n) = Sum_{k=1..n} n^k. 9
0, 1, 6, 39, 340, 3905, 55986, 960799, 19173960, 435848049, 11111111110, 313842837671, 9726655034460, 328114698808273, 11966776581370170, 469172025408063615, 19676527011956855056, 878942778254232811937, 41660902667961039785742, 2088331858752553232964199 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Sum of lengths of longest ending contiguous subsequences with the same value over all s in {1,...,n}^n: a(n) = Sum_{k=1..n} k*A228273(n,k). a(2) = 6 = 2+1+1+2: [1,1], [1,2], [2,1], [2,2]. - Alois P. Heinz, Aug 19 2013

a(n) is the expected wait time to see the contiguous subword 11...1 (n copies of 1) over all infinite sequences on alphabet {1,2,...,n}. - Geoffrey Critzer, May 19 2014

a(n) is the number of sequences of k elements from {1,2,...,n}, where 1<=k<=n. For example, a(2) = 6, counting the sequences, [1], [2], [1,1], [1,2], [2,1], [2,2]. Equivalently, a(n) is the number of bargraphs having width at most n and having height at most n. - Emeric Deutsch, Jan 24 2017.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..386

A. Blecher, C. Brennan, A. Knopfmacher and H. Prodinger, The height and width of bargraphs, Discrete Applied Math. 180, (2015), 36-44.

FORMULA

a(0)=0, a(1)=1; for n>1 a(n) = (n^(n+1)-1)/(n-1) - 1. - Benoit Cloitre, Aug 17 2002

a(n) = A031973(n)-1 for n>0. - Robert G. Wilson v, Apr 15 2015

MAPLE

a:= n-> `if`(n<2, n, (n^(n+1)-n)/(n-1)):

seq(a(n), n=0..20);  # Alois P. Heinz, Aug 15 2013

MATHEMATICA

f[n_]:=Sum[n^k, {k, n}]; Array[f, 30] (* Vladimir Joseph Stephan Orlovsky, Feb 14 2011*)

PROG

(Haskell)

a031972 n = sum $ take n $ iterate (* n) n

-- Reinhard Zumkeller, Nov 22 2014

(MAGMA) [1] cat [(n^(n+1)-n)/(n-1): n in [2..20]]; // Vincenzo Librandi, Apr 16 2015

CROSSREFS

Main diagonal of A228275.

Cf. A031973, A228273.

Sequence in context: A113347 A265953 A246571 * A308861 A124577 A006678

Adjacent sequences:  A031969 A031970 A031971 * A031973 A031974 A031975

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Dec 11 1999

EXTENSIONS

a(0)=0 prepended by Alois P. Heinz, Oct 22 2019

STATUS

approved

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Last modified November 14 04:56 EST 2019. Contains 329110 sequences. (Running on oeis4.)