

A001462


Golomb's sequence: a(n) is the number of times n occurs, starting with a(1) = 1.
(Formerly M0257 N0091)


56



1, 2, 2, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18, 19
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OFFSET

1,2


COMMENTS

It is understood that a(n) is taken to be the smallest number >= a(n1) which is compatible with the description.
Also called Silverman's sequence.
Vardi gives several identities satisfied by A001463 and this sequence.
We can interpret A001462 as a triangle: start with 1; 2,2; 3,3; and proceed by letting the row sum of row m1 be the number of elements of row m. The partial sums of the row sums give 1, 5, 11, 38, 272, ... Conjecture: this proceeds as Lionel Levile's sequence A014644. See also A113676.  Floor van Lamoen, Nov 06 2005.
The g.f. z*(1+z**4+z**7z**8+z**9z**3zz**11+z**12)/(1+z)/(z**2+1)/(z1)**2 conjectured by Simon Plouffe in his 1992 dissertation is wrong.  N. J. A. Sloane, May 13 2008
a(A095114(n)) = n and a(m) < m for m < A095114(n).  Reinhard Zumkeller, Feb 09 2012


REFERENCES

G. Everest, A. van der Poorten, I. Shparlinski and T. Ward, Recurrence Sequences, Amer. Math. Soc., 2003; p. 10.
S. W. Golomb, Problem 5407, Amer. Math. Monthly, 73 (1966), 674.
R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics. AddisonWesley, Reading, MA, 1990, p. 66.
J. Grytczuk, Another variation on Conway's recursive sequence, Discr. Math. 282 (2004), 149161.
R. K. Guy, Unsolved Problems in Number Theory, E25.
D. Marcus and N. J. Fine, Solutions to Problem 5407, Amer. Math. Monthly 74 (1967), 740743.
Petermann, Y.F. S., On Golomb's selfdescribing sequence, J. Number Theory 53 (1995), 1324.
Petermann, Y.F. S., On Golomb's selfdescribing sequence, II, Arch. Math. (Basel) 67 (1996), 473477.
Petermann, Y.F. S., Is the error term wild enough? Analysis (Munich) 18 (1998), 245256.
Petermann, Y.F. S. and Remy, JeanLuc, Golomb's selfdescribed sequence and functionaldifferential equations, Illinois J. Math. 42 (1998), 420440.
J. L. Remy, J. Number Theory, 66 (1997), 128.
J. Sauerberg and L. Shu, The long and the short on counting sequences, Amer. Math. Monthly, 104 (1997), 306317.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane, Seven Staggering Sequences, in Homage to a Pied Puzzler, E. Pegg Jr., A. H. Schoen and T. Rodgers (editors), A. K. Peters, Wellesley, MA, 2009, pp. 93110.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
I. Vardi, The error term in Golomb's sequence, J. Number Theory, 40 (1992), 111. (See also the Math. Review, 93d:11103)


LINKS

T. D. Noe, Table of n, a(n) for n = 1..10000
B. Cloitre, N. J. A. Sloane and M. J. Vandermast, Numerical analogues of Aronson's sequence, J. Integer Seqs., Vol. 6 (2003), #03.2.2.
B. Cloitre, N. J. A. Sloane and M. J. Vandermast, Numerical analogues of Aronson's sequence (math.NT/0305308)
Brady Haran and Tony Padilla, Six Sequences  Numberphile (2013).
Christian Perfect, Integer sequence reviews on Numberphile (or vice versa), 2013.
Y.F. S. Petermann, J.L. Remy and I. Vardi, Discrete derivatives of sequences, Adv. in Appl. Math. 27 (2001), 56284.
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, My favorite integer sequences, in Sequences and their Applications (Proceedings of SETA '98).
N. J. A. Sloane, Seven Staggering Sequences.
Eric Weisstein's World of Mathematics, Silverman's Sequence
Index entries for "core" sequences
Index entries for sequences of the a(a(n)) = 2n family


FORMULA

a(n) = phi^(2phi)*n^(phi1) + E(n), where phi is the golden number (1+sqrt(5))/2 (Marcus and Fine) and E(n) is an error term which Vardi shows is O( n^(phi1) / log n ).
a(1) = 1; a(n+1) = 1 + a(n+1a(a(n))).  Colin Mallows
a(1)=1, a(2)=2 and for a(1)+a(2)+..+a(n1) < k <= a(1)+a(2)+...+a(n) we have a(k)=n.  Benoit Cloitre, Oct 07 2003
G.f.: Sum_{k>0} x^a(k).  Michael Somos, Oct 21 2006


EXAMPLE

a(1) = 1, so 1 only appears once. The next term is therefore 2, which means 2 appears twice and so a(3) is also 2 but a(4) must be 3. And so on.


MAPLE

N:= 10000: A001462[1]:= 1: B[1]:= 1: A001462[2]:= 2:
for n from 2 while B[n1] <= N do
B[n]:= B[n1] + A001462[n];
for j from B[n1]+1 to B[n] do A001462[j]:= n end do
end do:
seq(A001462[j], j=1..N); # Robert Israel, Oct 30 2012


MATHEMATICA

a[1] = 1; a[n_] := a[n] = 1 + a[n  a[a[n  1]]]; Table[ a[n], {n, 84}] (* Robert G. Wilson v, Aug 26 2005 *)


PROG

(PARI) a=[ 1, 2, 2 ]; for(n=3, 20, for(i=1, a[ n ], a=concat(a, n))); a
(PARI) A001462(n)={ local(A, t, i); if(n<3, max(0, n), A=vector(n); t=A[i=2]=2; for(k=3, n, A[k]=A[k1]+if(t==0, t=A[i++ ]; 1)); A[n])} /* Michael Somos, Oct 21 2006 */
(MAGMA) [ n eq 1 select 1 else 1+Self(nSelf(Self(n1))) : n in [1..100] ]; // Sergei Haller (sergei(AT)sergeihaller.de), Dec 21 2006
(Haskell)
a001462 n = a001462_list !! (n1)
a001462_list = 1 : 2 : 2 : g 3 where
g x = (replicate (a001462 x) x) ++ g (x + 1)
 Reinhard Zumkeller, Feb 09 2012


CROSSREFS

Cf. A000002, A001463 (partial sums).
Sequence in context: A232753 A067085 A055086 * A082462 A005041 A030530
Adjacent sequences: A001459 A001460 A001461 * A001463 A001464 A001465


KEYWORD

easy,nonn,nice,core


AUTHOR

N. J. A. Sloane


STATUS

approved



