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.

A160711 Cyclops squares: squares (A000290) that are also cyclops numbers (A134808).

Original entry on oeis.org

0, 11025, 19044, 21025, 24025, 32041, 38025, 42025, 47089, 51076, 58081, 59049, 65025, 66049, 67081, 75076, 87025, 93025, 1110916, 1140624, 1170724, 1190281, 1240996, 1270129, 1290496, 1340964, 1350244, 1380625, 1420864, 1430416
Offset: 1

Views

Author

Omar E. Pol, Jun 08 2009

Keywords

Examples

			19044 is in the sequence because it is a square (138^2) and is also a cyclops number (odd number of digits, middle digit is the only zero).
11025 is in the sequence because it is a square (105^2) and is also a cyclops number (odd number of digits, middle digit is the only zero). - _Michael B. Porter_, Jul 09 2016
		

Crossrefs

Programs

  • Mathematica
    Select[Range[0, 1200]^2, And[OddQ@ Length@ #, #[[Ceiling[Length[#]/2]]] == 0, Count[#, 0] == 1] &@ IntegerDigits@ # &] (* Michael De Vlieger, Jul 08 2016 *)
    cnQ[n_]:=Module[{len=IntegerLength[n]},OddQ[len]&&DigitCount[n,10,0]==1 && IntegerDigits[n][[(len+1)/2]]==0]; Join[{0},Select[Range[1200]^2,cnQ]] (* Harvey P. Dale, Mar 19 2018 *)

A134146 Triangle of numbers obtained from the partition array A134145.

Original entry on oeis.org

1, 3, 1, 15, 3, 1, 105, 24, 3, 1, 945, 150, 24, 3, 1, 10395, 1485, 177, 24, 3, 1, 135135, 14805, 1620, 177, 24, 3, 1, 2027025, 191520, 16425, 1701, 177, 24, 3, 1, 34459425, 2687580, 208125, 16830, 1701, 177, 24, 3, 1, 654729075, 44552025, 2880360, 212985
Offset: 1

Views

Author

Wolfdieter Lang, Nov 13 2007

Keywords

Comments

This triangle is named S2(3)'.
In the same manner the unsigned Lah triangle A008297 is obtained from the partition array A130561.

Examples

			[1]; [3,1]; [15,3,1]; [105,24,3,1]; [945,150,24,3,1];...
		

Crossrefs

Cf. A134147 (row sums).
Cf. A134148 (allternating row sums).
Cf. A134134 (k=2 member of this triangle family).

Formula

a(n,m)=sum(product(S2(3;j,1)^e(n,m,q,j),j=1..n),q=1..p(n,m)) if n>=m>=1, else 0. Here p(n,m)=A008284(n,m), the number of m parts partitions of n and e(n,m,q,j) is the exponent of j in the q-th m part partition of n. S2(3;j,1)= A001147(j) = A035342(j,1) = (2*j-1)!!.

A160712 Composite cyclops numbers (A134808).

Original entry on oeis.org

102, 104, 105, 106, 108, 201, 202, 203, 204, 205, 206, 207, 208, 209, 301, 302, 303, 304, 305, 306, 308, 309, 402, 403, 404, 405, 406, 407, 408, 501, 502, 504, 505, 506, 507, 508, 602, 603, 604, 605, 606, 608, 609, 702, 703, 704
Offset: 1

Views

Author

Omar E. Pol, Jun 08 2009

Keywords

Crossrefs

Extensions

Edited by Omar E. Pol, Jul 04 2009

A134147 Row sums of triangle A134146 and partition array A134145 (M3(3)/M3).

Original entry on oeis.org

1, 4, 19, 133, 1123, 12085, 151765, 2236876, 37373866, 702393424, 14611910794, 333811635793, 8298224157103, 223061783080075, 6444694333816630, 199168434836797921, 6555131451981351961, 228906927287899911709
Offset: 1

Views

Author

Wolfdieter Lang, Nov 13 2007

Keywords

Crossrefs

Cf. A000041, A134148 (alternating row sums of triangle A134146).

Formula

a(n) = Sum_{m=1..n} A134146(n,m), n>=1.
a(n) = Sum_{k=1..p(n)} A134145(n,k), with p(n) = A000041(n) (number of partitions of n).
Showing 1-4 of 4 results.