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A003261 Woodall (or Riesel) numbers: n*2^n - 1.
(Formerly M4379)
1, 7, 23, 63, 159, 383, 895, 2047, 4607, 10239, 22527, 49151, 106495, 229375, 491519, 1048575, 2228223, 4718591, 9961471, 20971519, 44040191, 92274687, 192937983, 402653183, 838860799, 1744830463, 3623878655, 7516192767 (list; graph; refs; listen; history; text; internal format)



For n>1, a(n) is base at which zero is reached for the function "write f(j) in base j, read as base j+1 and then subtract 1 to give f(j+1)" starting from f(n) = n^2 - 1. - Henry Bottomley, Aug 06 2000

Sequence corresponds also to the maximum chain length of the classic puzzle whereby, under agreed commercial terms, an asset of unringed golden chain, when judiciously fragmented into as few as n pieces and n-1 opened links (through n-1 cuts), might be used to settle debt sequentially, with a golden link covering for unit cost. Here beside the n-1 opened links, the n fragmented pieces have lengths n, 2*n, 4*n, ..., 2^(n-1)*n. For instance, the chain of original length a(5)=159, if segregated by 4 cuts into 5+1+10+1+20+1+40+1+80, may be used to pay sequentially, i.e., a link-cost at a time, for an equivalent cost up to 159 links, to the same creditor. - Lekraj Beedassy, Feb 06 2003


A. Brousseau, Number Theory Tables. Fibonacci Association, San Jose, CA, 1973, p. 159.

K. R. Bhutani and A. B. Levin, "The Problem of Sawing a Chain", Journal of Recreational Mathematics 2002-3 31(1) 32-35.

G. Everest, A. van der Poorten, I. Shparlinski and T. Ward, Recurrence Sequences, Amer. Math. Soc., 2003; see esp. p. 255.

M. Gardner, Martin Gardner's Sixth Book of Mathematical Diversions from Scientific American, "Gold Links", Problem 4, pp. 50-51; 57-58, University of Chicago Press, 1983.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


T. D. Noe, Table of n, a(n) for n = 1..300

Ray Ballinger, Woodall Primes: Definition and Status

Alfred Brousseau, Fibonacci and Related Number Theoretic Tables, Fibonacci Association, San Jose, CA, 1972. See p. 159.

C. K. Caldwell, Woodall Numbers

Paul Leyland, Factors of Cullen and Woodall numbers

Paul Leyland, Generalized Cullen and Woodall numbers

D. Marques, On Generalized Cullen and Woodall Numbers That are Also Fibonacci Numbers, Journal of Integer Sequences, 17 (2014), #14.9.4.

Hisanori Mishima, Factorizations of many number sequences: Riesel numbers, n=1..100, n=101..200, n=201..300, n=301..323.

Simon Plouffe, Approximations de séries génératrices et quelques conjectures, Dissertation, Université du Québec à Montréal, 1992.

Simon Plouffe, 1031 Generating Functions, Appendix to Thesis, Montreal, 1992

T. Sillke, Using Chains Links To Pay For A Room

Amelia Carolina Sparavigna, On the generalized sums of Mersenne, Fermat, Cullen and Woodall Numbers, Politecnico di Torino (Italy, 2019).

Amelia Carolina Sparavigna, Composition Operations of Generalized Entropies Applied to the Study of Numbers, International Journal of Sciences (2019) Vol. 8, No. 4, 87-92.

Amelia Carolina Sparavigna, The groupoids of Mersenne, Fermat, Cullen, Woodall and other Numbers and their representations by means of integer sequences, Politecnico di Torino, Italy (2019), [math.NT].

Amelia Carolina Sparavigna, Some Groupoids and their Representations by Means of Integer Sequences, International Journal of Sciences (2019) Vol. 8, No. 10.

Eric Weisstein's World of Mathematics, Woodall Number.

Wikipedia, Woodall number

Index entries for linear recurrences with constant coefficients, signature (5,-8,4).


G.f.: x*(-1-2*x+4*x^2) / ( (x-1)*(-1+2*x)^2 ). - Simon Plouffe in his 1992 dissertation

Binomial transform of A133653 and double binomial transform of [1, 5, -1, 1, -1, 1, ...]. - Gary W. Adamson, Sep 19 2007

a(n) = -(2)^n * A006127(-n) for all n in Z. - Michael Somos, Nov 04 2018


G.f. = x + 7*x^2 + 23*x^3 + 63*x^4 + 159*x^5 + 383*x^6 + 895*x^7 + ... - Michael Somos, Nov 04 2018


Table[n*2^n-1, {n, 3*4!}] (* Vladimir Joseph Stephan Orlovsky, Apr 25 2010 *)



a003261 = (subtract 1) . a036289  -- Reinhard Zumkeller, Mar 05 2012

(PARI) A003261(n)=n*2^n-1  \\ M. F. Hasler, Oct 31 2012

(MAGMA) [n*2^n -1: n in [1..30]]; // G. C. Greubel, Nov 04 2018

(Python) [n*2**n - 1 for n in range(1, 29)] # Michael S. Branicky, Jan 07 2021


Cf. A002234, A002064, A005849, A050918, A006127.

a(n) = A036289(n) - 1 = A002064(n) - 2.

Cf. A133653.

Sequence in context: A201110 A333187 A220509 * A306971 A266801 A066187

Adjacent sequences:  A003258 A003259 A003260 * A003262 A003263 A003264




N. J. A. Sloane



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Last modified February 28 01:56 EST 2021. Contains 341695 sequences. (Running on oeis4.)