A124798 -id:A124798 - cp's OEIS frontend

A103372 a(1) = a(2) = a(3) = a(4) = a(5) = 1 and for n>5: a(n) = a(n-4) + a(n-5).

1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 4, 4, 4, 5, 7, 8, 8, 9, 12, 15, 16, 17, 21, 27, 31, 33, 38, 48, 58, 64, 71, 86, 106, 122, 135, 157, 192, 228, 257, 292, 349, 420, 485, 549, 641, 769, 905, 1034, 1190, 1410, 1674, 1939, 2224, 2600, 3084, 3613, 4163, 4824, 5684, 6697, 7776

Offset: 1

Jonathan Vos Post, Feb 03 2005

k=4 case of the family of sequences whose k=1 case is the Fibonacci sequence A000045, k=2 case is the Padovan sequence A000931 (offset so as to begin 1,1,1) and k=3 case is A079398 (offset so as to begin 1,1,1,1).
The general case for integer k>1 is defined: a(1) = a(2) = ... = a(k+1) and for n>(k+1) a(n) = a(n-k) + a(n-[k+1]).
For this k=4 case, the ratio of successive terms a(n)/a(n-1) approaches the unique positive root of the irreducible characteristic polynomial: x^5 - x - 1 = 0, A160155.
The sequence of prime values in this k=4 case is A103382; The sequence of semiprime values in this k=4 case is A103392.

			a(14) = 5 because a(14) = a(14-4) + a(14-5) = a(10) + a(9) = 3 + 2 = 5.

Zanten, A. J. van, The golden ratio in the arts of painting, building and mathematics, Nieuw Archief voor Wiskunde, 4 (17) (1999) 229-245.

Indranil Ghosh, Table of n, a(n) for n = 1..14857
J.-P. Allouche and T. Johnson, Narayana's cows and delayed morphisms, in G. Assayag, M. Chemillier, and C. Eloy, Troisièmes Journées d'Informatique Musicale, JIM '96, Île de Tatihou, France, 1996, pp. 2-7. [The hal link does not always work. - _N. J. A. Sloane_, Feb 19 2025]
J.-P. Allouche and T. Johnson, Narayana's cows and delayed morphisms, in G. Assayag, M. Chemillier, and C. Eloy, Troisièmes Journées d'Informatique Musicale, JIM '96, Île de Tatihou, France, 1996, pp. 2-7. [Local copy with annotations and a correction from _N. J. A. Sloane_, Feb 19 2025]
Richard Padovan, Dom Hans van der Laan and the Plastic Number.
E. S. Selmer, On the irreducibility of certain trinomials, Math. Scand., 4 (1956) 287-302.
J. Shallit, A generalization of automatic sequences, Theoretical Computer Science, 61 (1988), 1-16.
Index entries for linear recurrences with constant coefficients, signature (0,0,0,1,1).

Cf. A000931, A079398, A103373-A103380, A103382, A103392.

k = 4; Do[a[n] = 1, {n, k + 1}]; a[n_] := a[n] = a[n - k] + a[n - k - 1]; Array[a, 61]
LinearRecurrence[{0,0,0,1,1},{1,1,1,1,1},70] (* Harvey P. Dale, Apr 22 2015 *)

a(n)=([0,1,0,0,0; 0,0,1,0,0; 0,0,0,1,0; 0,0,0,0,1; 1,1,0,0,0]^(n-1)*[1;1;1;1;1])[1,1] \\ Charles R Greathouse IV, Oct 03 2016

G.f. -x*(1+x)*(1+x^2) / ( -1+x^4+x^5 ). - R. J. Mathar, Aug 26 2011

a(n) = A124789(n-2)+A124798(n-1). - R. J. Mathar, Jun 30 2020

Edited by Ray Chandler and Robert G. Wilson v, Feb 06 2005

A124797 Sum of cyclic permutations of 123...n seen as number written in base n+1: ((n+1)^n-1)*(n+1)/2.

Original entry on oeis.org

1, 12, 126, 1560, 23325, 411768, 8388604, 193710240, 4999999995, 142655835300, 4458050224122, 151437553296120, 5556003412779001, 218946945190429680, 9223372036854775800, 413620130943168382080, 19673204037648268787703

Offset: 1

M. F. Hasler, Nov 07 2006

Sequence A083956 becomes "unnatural" for n>9. The present sequence is more universal since 10 is not singled out as a particular value. See A124798 for the sequence of digits of a(n) in base n+1 and for more results.

			a(2) = 12[3] + 21[3] = 110[3] = 12[10] where [b] indicates the basis b in which the number is written;
a(3) = 123[4] + 231[4] + 312[4] = 126[10];
a(4) = 1234[5] + 2341[5] + 3412[5] + 4123[5] = 22220[5] = 1560[10],...

Vincenzo Librandi, Table of n, a(n) for n = 1..200

Cf. A083956, A124798.

[((n + 1)^n - 1)*(n + 1) div 2: n in [1..20]]; // Vincenzo Librandi, Jan 09 2013

a:=proc(n) local b,m,i,s; b:=n+1: m:=add(i*b^(n-i),i=1..n): s:=m: for i to n-1 do m:=b^(n-1)*modp(m,b)+iquo(m,b): s:=s+m: od: s end; # or simply # a := n -> (n+1)/2*((n+1)^n-1)

Table[((n+1)^n-1)*(n+1)/2, {n,22}] (* Vladimir Joseph Stephan Orlovsky, Dec 28 2010 *)

a(n) = (n+1)/2*((n+1)^n-1).

cp's OEIS Frontend

A103372 a(1) = a(2) = a(3) = a(4) = a(5) = 1 and for n>5: a(n) = a(n-4) + a(n-5).

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