cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-4 of 4 results.

A333405 Number of integers in base n having exactly three distinct digits such that the number formed by the consecutive subsequence of the initial j digits is divisible by j for all j in {1,2,3}.

Original entry on oeis.org

0, 0, 0, 0, 5, 6, 18, 33, 50, 67, 115, 134, 206, 258, 340, 398, 537, 598, 778, 891, 1086, 1209, 1487, 1614, 1950, 2148, 2504, 2716, 3181, 3398, 3938, 4245, 4810, 5135, 5835, 6166, 6958, 7398, 8220, 8682, 9665, 10134, 11226, 11823, 12950, 13573, 14887, 15518
Offset: 0

Views

Author

Alois P. Heinz, May 04 2020

Keywords

Examples

			a(4) = 5: 102, 120, 123, 201, 321 (written in base 4).
a(5) = 6: 132, 201, 204, 314, 402, 421 (written in base 5).
a(6) = 18: 103, 120, 123, 140, 143, 203, 240, 243, 320, 340, 403, 420, 423, 503, 520, 523, 540, 543 (written in base 6).
		

Crossrefs

Column k=3 of A334318.

Formula

G.f.: (2*x^11+5*x^9+10*x^8+21*x^6+2*x^5+5*x^4+14*x^3+7*x^2+x+5)*x^4 / ((x^2+x+1)^2 *(x^2-x+1)^2 *(x+1)^3 *(x-1)^4).

A333469 Number of integers in base n having exactly four distinct digits such that the number formed by the consecutive subsequence of the initial j digits is divisible by j for all j in {1,2,3,4}.

Original entry on oeis.org

0, 0, 0, 0, 2, 1, 8, 34, 58, 98, 168, 275, 428, 586, 849, 1193, 1647, 2017, 2679, 3454, 4410, 5283, 6676, 7900, 9838, 11396, 13758, 15994, 19216, 21493, 25450, 29026, 33854, 37636, 43724, 48369, 55884, 61374, 69831, 76803, 87269, 94285, 106337, 116062, 129862
Offset: 0

Views

Author

Alois P. Heinz, May 04 2020

Keywords

Examples

			a(4) = 2: 1230, 3210 (written in base 4).
a(5) = 1: 3140 (written in base 5).
a(6) = 6: 1032, 1204, 1432, 3204, 4032, 5032, 5204, 5432 (written in base 6).
		

Crossrefs

Column k=4 of A334318.

Programs

  • Mathematica
    LinearRecurrence[{1,1,-1,0,0,0,0,0,0,0,0,3,-3,-3,3,0,0,0,0,0,0,0,0,-3,3,3,-3,0,0,0,0,0,0,0,0,1,-1,-1,1},{0,0,0,0,2,1,8,34,58,98,168,275,428,586,849,1193,1647,2017,2679,3454,4410,5283,6676,7900,9838,11396,13758,15994,19216,21493,25450,29026,33854,37636,43724,48369,55884,61374,69831,76803},110] (* Harvey P. Dale, Oct 06 2023 *)

Formula

G.f.: -(6*x^35 -4*x^33 +41*x^32 +11*x^31 +87*x^30 -46*x^29 +40*x^28 +165*x^27 +126*x^26 -40*x^25 +293*x^24 +120*x^23 +94*x^22 +181*x^21 +296*x^20 +150*x^19 +299*x^18 +56*x^17 +243*x^16 +324*x^15 +193*x^14 +29*x^13 +185*x^12 +186*x^11 +110*x^10 +51*x^9 +83*x^8 +67*x^7 +46*x^6 +14*x^5 +17*x^4 +27*x^3 +5*x^2 -x +2)*x^4 / ((x^2+1)^3 *(x^2+x+1)^3 *(x^2-x+1)^3 *(x^4-x^2+1)^3 *(x+1)^4 *(x-1)^5).

A334320 Number of even integers in base n with exactly two distinct digits.

Original entry on oeis.org

0, 0, 1, 1, 5, 6, 13, 15, 25, 28, 41, 45, 61, 66, 85, 91, 113, 120, 145, 153, 181, 190, 221, 231, 265, 276, 313, 325, 365, 378, 421, 435, 481, 496, 545, 561, 613, 630, 685, 703, 761, 780, 841, 861, 925, 946, 1013, 1035, 1105, 1128, 1201, 1225, 1301, 1326, 1405
Offset: 0

Views

Author

Alois P. Heinz, Apr 22 2020

Keywords

Examples

			a(4) = 5: 10, 12, 20, 30, 32 (written in base 4).
a(7) = 15: 13, 15, 20, 24, 26, 31, 35, 40, 42, 46, 51, 53, 60, 62, 64 (written in base 7).
		

Crossrefs

Column k=2 of A334318.

Formula

G.f.: -(x^3+2*x^2+1)*x^2/((x+1)^2*(x-1)^3).
a(n) = A334318(n,2).

A334319 Number of integers m in base n with distinct digits such that the number formed by the consecutive subsequence of the initial j digits is divisible by j for all j in {1,...,length(m)}.

Original entry on oeis.org

1, 3, 4, 16, 18, 54, 112, 225, 397, 707, 1566, 2664, 6960, 9213, 23066, 39980, 100239, 116229, 455539, 465054, 1157163, 2064246, 6735123, 4609476, 22943866, 27085154, 64108419, 76354062, 420698429, 180541932, 1833215296, 1057775180, 3361833346, 5293490772, 14955881506, 7186246508
Offset: 1

Views

Author

Alois P. Heinz, Apr 22 2020

Keywords

Crossrefs

Row sums of A334318.

Programs

  • Maple
    b:= proc(n, s, w) option remember; `if`(s={}, 0, (k-> add((t->
          `if`(t=0, 1, `if`(irem(t, k)=0, b(n, s minus {j}, t)
              +1, 0)))(w*n+j), j=s)))(1+n-nops(s))
        end:
    a:= n-> b(n, {$0..n-1}, 0):
    seq(a(n), n=1..18);

Extensions

a(27)-a(36) from Giovanni Resta, May 04 2020
Showing 1-4 of 4 results.