A015446 -id:A015446 - cp's OEIS frontend

A161999 For n even a(n) = a(n-1) + 10*a(n-2), for n odd a(n) = a(n-3) + 10 a(n-2); with a(1) = 0, a(2) = 1.

0, 1, 1, 10, 20, 101, 301, 1030, 4040, 10601, 51001, 110050, 620060, 1151501, 7352101, 12135070, 85656080, 128702801, 985263601, 1372684090, 11225320100, 14712104501, 126965305501, 158346365110, 1427999420120

Offset: 1

Mark Dols, Jun 24 2009, Jun 28 2009, Jul 13 2009

			As pairs:
0, 1
1, 10
20, 101
301, 1030
4040, 10601
51001, 110050
620060, 1151501
7352101, 12135070
85656080, 128702801

Harvey P. Dale, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (0, 20, 0, -99).

Combination of A081192 and A016190. Triangle A007318 (even /uneven rows). Partly same function as A015446. A001020 (as sum of pairs of 2n).A001019 (as difference of pairs of 2n)

Cf. A162849.

nxt[{n_,a_,b_,c_}]:={n+1,b,c,If[OddQ[n],c+10b,a+10b]}; NestList[nxt,{2,0,1,1},30][[All,2]] (* or *) LinearRecurrence[{0,20,0,-99},{0,1,1,10},30] (* Harvey P. Dale, May 03 2018 *)

a(n)=20*a(n-2)-99*a(n-4). G.f.: -x^2*(-1-x+10*x^2)/((3*x-1)*(3*x+1)*(11*x^2-1)). [From R. J. Mathar, Jul 13 2009]

Edited by N. J. A. Sloane, Jun 30 2009

NAME adapted to offset. - R. J. Mathar, Jun 19 2021

A317054 Triangle read by rows: T(0,0) = 1; T(n,k) = T(n-1,k) + 10 * T(n-2,k-1) for k = 0..floor(n/2); T(n,k)=0 for n or k < 0.

Original entry on oeis.org

1, 1, 1, 10, 1, 20, 1, 30, 100, 1, 40, 300, 1, 50, 600, 1000, 1, 60, 1000, 4000, 1, 70, 1500, 10000, 10000, 1, 80, 2100, 20000, 50000, 1, 90, 2800, 35000, 150000, 100000, 1, 100, 3600, 56000, 350000, 600000, 1, 110, 4500, 84000, 700000, 2100000, 1000000, 1, 120, 5500, 120000, 1260000, 5600000, 7000000

Offset: 0

Zagros Lalo, Jul 20 2018

The numbers in rows of the triangle are along skew diagonals pointing top-right in center-justified triangle given in A013617 ((1+10x)^n) and along skew diagonals pointing top-left in center-justified triangle given in A038303 ((10+x)^n).
The coefficients in the expansion of 1/(1-x-10*x^2) are given by the sequence generated by the row sums.
The row sums are Generalized Fibonacci numbers (see A015446).
If s(n) is the row sum at n, then the ratio s(n)/s(n-1) is approximately 3.701562118716424343244... ((1+sqrt(41))/2), when n approaches infinity.

			Triangle begins:
  1;
  1;
  1, 10;
  1, 20;
  1, 30, 100;
  1, 40, 300;
  1, 50, 600, 1000;
  1, 60, 1000, 4000;
  1, 70, 1500, 10000, 10000;
  1, 80, 2100, 20000, 50000;
  1, 90, 2800, 35000, 150000, 100000;
  1, 100, 3600, 56000, 350000, 600000;
  1, 110, 4500, 84000, 700000, 2100000, 1000000;
  1, 120, 5500, 120000, 1260000, 5600000, 7000000;

Shara Lalo and Zagros Lalo, Polynomial Expansion Theorems and Number Triangles, Zana Publishing, 2018, ISBN: 978-1-9995914-0-3, pp. 70, 102.

Zagros Lalo, Left-justified triangle
Zagros Lalo, Skew diagonals in center-justified triangle of coefficients in expansion of (1 + 10x)^n
Zagros Lalo, Skew diagonals in center-justified triangle of coefficients in expansion of (10 + x)^n

Row sums give A015446.

Cf. A013617, A038303.

t[0, 0] = 1; t[n_, k_] := If[n < 0 || k < 0, 0, t[n - 1, k] + 10 t[n - 2, k - 1]]; Table[t[n, k], {n, 0, 13}, {k, 0, Floor[n/2]}] // Flatten
Table[10^k Binomial[n - k, k], {n, 0, 13}, {k, 0, Floor[n/2]}] // Flatten

T(n, k) = if ((n<0) || (k<0), 0, if ((n==0) && (k==0), 1, T(n-1, k)+10*T(n-2, k-1)));
tabf(nn) = for (n=0, nn, for (k=0, n\2, print1(T(n, k), ", ")); print); \\ Michel Marcus, Jul 20 2018

A162671 For n even a(n) = a(n-1) + a(n-2), for n odd a(n) = 100*a(n-1) + a(n-2), with a(0) = 0, a(1) = 1.

Original entry on oeis.org

0, 1, 1, 101, 102, 10301, 10403, 1050601, 1061004, 107151001, 108212005, 10928351501, 11036563506, 1114584702101, 1125621265607, 113676711262801, 114802332528408, 11593909964103601, 11708712296632009, 1182465139627304501, 1194173851923936510, 120599850332020955501

Offset: 0

Mark Dols, Jul 10 2009

Index entries for linear recurrences with constant coefficients, signature (0,102,0,-1).

Partly same as A041059 (and its palindromic partner-sequence A015446). A007318.

a:= proc(n) a(n):= `if`(n<2, n, a(n-1)*(1+99*(n mod 2))+a(n-2)) end:
seq(a(n), n=0..22);  # Alois P. Heinz, Jan 20 2025

LinearRecurrence[{0,102,0,-1},{1,1,101,102},20] (* Harvey P. Dale, May 08 2020 *)

a(n) = 102*a(n-2)-a(n-4). G.f.: x*(1+x-x^2)/((x^2+10*x-1)*(x^2-10*x-1)). - R. J. Mathar, Jul 14 2009

More terms from R. J. Mathar, Jul 14 2009

A242763 a(n) = 1 for n <= 7; a(n) = a(n-5) + a(n-7) for n>7.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 4, 4, 4, 5, 5, 7, 7, 8, 9, 9, 12, 12, 15, 16, 17, 21, 21, 27, 28, 32, 37, 38, 48, 49, 59, 65, 70, 85, 87, 107, 114, 129, 150, 157, 192, 201, 236, 264, 286, 342, 358, 428, 465, 522, 606, 644, 770, 823, 950, 1071, 1166, 1376

Offset: 1

Vicente Jesús Maniega Granado, Oct 03 2016

Generalized Fibonacci growth sequence using i = 2 as maturity period, j = 5 as conception period, and k = 2 as growth factor.

Maturity period is the number of periods that a Fibonacci tree node needs for being able to start developing branches. Conception period is the number of periods in a Fibonacci tree node needed to develop new branches since its maturity. Growth factor is the number of additional branches developed by a Fibonacci tree node, plus 1, and equals the base of the exponential series related to the given tree if maturity factor would be zero. Standard Fibonacci would use 1 as maturity period, 1 as conception period, and 2 as growth factor as the series becomes equal to 2^n with a maturity period of 0. Related to Lucas sequences.

			For n = 13 the a(13) = a(8) + a(6) = 2 + 1 = 3.

Colin Barker, Table of n, a(n) for n = 1..1000
Julia Collins, Fibonacci Tree
Fractal Foundation, Fibonacci Fractals
D. H. Lehmer, An extended theory of Lucas' functions, Annals of Mathematics, Second Series, Vol. 31, No. 3 (Jul., 1930), pp. 419-448.
Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,1,0,1).

Cf. A000079 (i = 0, j = 1, k = 2), A000244 (i = 0, j = 1, k = 3), A000302 (i = 0, j = 1, k = 4), A000351 (i = 0, j = 1, k = 5), A000400 (i = 0, j = 1, k = 6), A000420 (i = 0, j = 1, k = 7), A001018 (i = 0, j = 1, k = 8), A001019 (i = 0, j = 1, k = 9), A011557 (i = 0, j = 1, k = 10), A001020 (i = 0, j = 1, k = 11), A001021 (i = 0, j = 1, k = 12), A016116 (i = 0, j = 2, k = 2), A108411 (i = 0, j = 2, k = 3), A213173 (i = 0, j = 2, k = 4), A074872 (i = 0, j = 2, k = 5), A173862 (i = 0, j = 3, k = 2), A127975 (i = 0, j = 3, k = 3), A200675 (i = 0, j = 4, k = 2), A111575 (i = 0, j = 4, k = 3), A000045 (i = 1, j = 1, k = 2), A001045 (i = 1, j = 1, k = 3), A006130 (i = 1, j = 1, k = 4), A006131 (i = 1, j = 1, k = 5), A015440 (i = 1, j = 1, k = 6), A015441 (i = 1, j = 1, k = 7), A015442 (i = 1, j = 1, k = 8), A015443 (i = 1, j = 1, k = 9), A015445 (i = 1, j = 1, k = 10), A015446 (i = 1, j = 1, k = 11), A015447 (i = 1, j = 1, k = 12), A000931 (i = 1, j = 2, k = 2), A159284 (i = 1, j = 2, k = 3), A238389 (i = 1, j = 2, k = 4), A097041 (i = 1, j = 2, k = 10), A079398 (i = 1, j = 3, k = 2), A103372 (i = 1, j = 4, k = 2), A103373 (i = 1, j = 5, k = 2), A103374 (i = 1, j = 6, k = 2), A000930 (i = 2, j = 1, k = 2), A077949 (i = 2, j = 1, k = 3), A084386 (i = 2, j = 1, k = 4), A089977 (i = 2, j = 1, k = 5), A178205 (i = 2, j = 1, k = 11), A103609 (i = 2, j = 2, k = 2), A077953 (i = 2, j = 2, k = 3), A226503 (i = 2, j = 3, k = 2), A122521 (i = 2, j = 6, k = 2), A003269 (i = 3, j = 1, k = 2), A052942 (i = 3, j = 1, k = 3), A005686 (i = 3, j = 2, k = 2), A237714 (i = 3, j = 2, k = 3), A238391 (i = 3, j = 2, k = 4), A247049 (i = 3, j = 3, k = 2), A077886 (i = 3, j = 3, k = 3), A003520 (i = 4, j = 1, k = 2), A108104 (i = 4, j = 2, k = 2), A005708 (i = 5, j = 1, k = 2), A237716 (i = 5, j = 2, k = 3), A005709 (i = 6, j = 1, k = 2), A122522 (i = 6, j = 2, k = 2), A005710 (i = 7, j = 1, k = 2), A237718 (i = 7, j = 2, k = 3), A017903 (i = 8, j = 1, k = 2).

[n le 7 select 1 else Self(n-5)+Self(n-7): n in [1..70]]; // Vincenzo Librandi, Nov 30 2016

LinearRecurrence[{0, 0, 0, 0, 1, 0, 1}, {1, 1, 1, 1, 1, 1, 1}, 70] (*  or *)
CoefficientList[ Series[(1+x+x^2+x^3+x^4)/(1-x^5-x^7), {x, 0, 70}], x] (* Robert G. Wilson v, Nov 25 2016 *)
nxt[{a_,b_,c_,d_,e_,f_,g_}]:={b,c,d,e,f,g,a+c}; NestList[nxt,{1,1,1,1,1,1,1},70][[;;,1]] (* Harvey P. Dale, Oct 22 2024 *)

Vec(x*(1+x+x^2+x^3+x^4)/((1-x+x^2)*(1+x-x^3-x^4-x^5)) + O(x^100)) \\ Colin Barker, Oct 27 2016

@CachedFunction # a = A242763
def a(n): return 1 if n<8 else a(n-5) +a(n-7)
[a(n) for n in range(1,76)] # G. C. Greubel, Oct 23 2024

Generic a(n) = 1 for n <= i+j; a(n) = a(n-j) + (k-1)*a(n-(i+j)) for n>i+j where i = maturity period, j = conception period, k = growth factor.
G.f.: x*(1+x+x^2+x^3+x^4) / ((1-x+x^2)*(1+x-x^3-x^4-x^5)). - Colin Barker, Oct 09 2016
Generic g.f.: x*(Sum_{l=0..j-1} x^l) / (1-x^j-(k-1)*x^(i+j)), with i > 0, j > 0 and k > 1.

cp's OEIS Frontend

A161999 For n even a(n) = a(n-1) + 10*a(n-2), for n odd a(n) = a(n-3) + 10 a(n-2); with a(1) = 0, a(2) = 1.

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A317054 Triangle read by rows: T(0,0) = 1; T(n,k) = T(n-1,k) + 10 * T(n-2,k-1) for k = 0..floor(n/2); T(n,k)=0 for n or k < 0.

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A162671 For n even a(n) = a(n-1) + a(n-2), for n odd a(n) = 100*a(n-1) + a(n-2), with a(0) = 0, a(1) = 1.

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A242763 a(n) = 1 for n <= 7; a(n) = a(n-5) + a(n-7) for n>7.

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A164827 Generalized Lucas numbers: a(n) = a(n-1) + 10*a(n-2); with a(1)=2 a(2)=1.

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