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.

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A195851 Column 7 of array A195825. Also column 1 of triangle A195841. Also 1 together with the row sums of triangle A195841.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 4, 4, 4, 4, 4, 5, 7, 10, 12, 13, 13, 13, 13, 14, 16, 21, 27, 32, 34, 35, 35, 36, 38, 44, 54, 67, 77, 83, 85, 87, 89, 95, 107, 128, 152, 173, 185, 192, 196, 203, 216, 242, 281, 328, 367, 394, 409, 421, 436, 465
Offset: 0

Views

Author

Omar E. Pol, Oct 07 2011

Keywords

Comments

Note that this sequence contains four plateaus: [1, 1, 1, 1, 1, 1, 1, 1], [4, 4, 4, 4, 4, 4], [13, 13, 13, 13], [35, 35]. For more information see A210843 and other sequences of this family. - Omar E. Pol, Jun 29 2012

Crossrefs

Programs

  • Maple
    A195160 := proc(n)
            (18*n*(n+1)+5*(2*n+1)*(-1)^n-5)/16 ;
    end proc:
    A195841 := proc(n, k)
            option remember;
            local ks, a, j ;
            if A195160(k) > n then
                    0 ;
            elif n <= 5 then
                    return 1;
            elif k = 1 then
                    a := 0 ;
                    for j from 1 do
                            if A195160(j) <= n-1 then
                                    a := a+procname(n-1, j) ;
                            else
                                    break;
                            end if;
                    end do;
                    return a;
            else
                    ks := A195160(k) ;
                    (-1)^floor((k-1)/2)*procname(n-ks+1, 1) ;
            end if;
    end proc:
    A195851 := proc(n)
            A195841(n+1,1) ;
    end proc:
    seq(A195851(n), n=0..60) ; # R. J. Mathar, Oct 08 2011

Formula

G.f.: Product_{k>=1} 1/((1 - x^(9*k))*(1 - x^(9*k-1))*(1 - x^(9*k-8))). - Ilya Gutkovskiy, Aug 13 2017
a(n) ~ exp(Pi*sqrt(2*n)/3) / (8*sin(Pi/9)*n). - Vaclav Kotesovec, Aug 14 2017

A196933 Column 9 of array A195825. Also column 1 of triangle A195843. Also 1 together with the row sums of triangle A195843.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 7, 10, 12, 13, 13, 13, 13, 13, 13, 14, 16, 21, 27, 32, 34, 35, 35, 35, 35, 36, 38, 44, 54, 67, 77, 83, 85, 86, 86, 87, 89, 95, 107, 128, 152, 173, 185, 191, 193, 195, 197, 203, 216, 242, 281
Offset: 0

Views

Author

Omar E. Pol, Oct 07 2011

Keywords

Comments

Note that this sequence contains five plateaus: [1, 1, 1, 1, 1, 1, 1, 1, 1, 1], [4, 4, 4, 4, 4, 4, 4, 4], [13, 13, 13, 13, 13, 13], [35, 35, 35, 35], [86, 86]. For more information see A210843 and other sequences of this family. - Omar E. Pol, Jun 29 2012

Crossrefs

Programs

  • Mathematica
    T := Product[1/((1 - x^(11*k))*(1 - x^(11*k - 1))*(1 - x^(11*k - 10))), {k, 1, 70}]; a:= CoefficientList[Series[T, {x, 0, 60}], x]; Table[a[[n]], {n, 1, 50}] (* G. C. Greubel, Jun 28 2018 *)

Formula

G.f.: Product_{k>=1} 1/((1 - x^(11*k))*(1 - x^(11*k-1))*(1 - x^(11*k-10))). - Ilya Gutkovskiy, Aug 13 2017
a(n) ~ exp(Pi*sqrt(2*n/11)) / (8*sin(Pi/11)*n). - Vaclav Kotesovec, Aug 14 2017

Extensions

More terms from Omar E. Pol, Jun 10 2012

A211970 Square array read by antidiagonal: T(n,k), n >= 0, k >= 0, which arises from a generalization of Euler's Pentagonal Number Theorem.

Original entry on oeis.org

1, 1, 1, 2, 1, 1, 4, 2, 1, 1, 6, 3, 1, 1, 1, 10, 5, 2, 1, 1, 1, 16, 7, 3, 1, 1, 1, 1, 24, 11, 4, 2, 1, 1, 1, 1, 36, 15, 5, 3, 1, 1, 1, 1, 1, 54, 22, 7, 4, 2, 1, 1, 1, 1, 1, 78, 30, 10, 4, 3, 1, 1, 1, 1, 1, 1, 112, 42, 13, 5, 4, 2, 1, 1, 1, 1, 1, 1
Offset: 0

Views

Author

Omar E. Pol, Jun 10 2012

Keywords

Comments

In the infinite square array if k is positive then column k is related to the generalized m-gonal numbers, where m = k+4. For example: column 1 is related to the generalized pentagonal numbers A001318. Column 2 is related to the generalized hexagonal numbers A000217 (note that A000217 is also the entry for the triangular numbers). And so on...
In the following table Euler's Pentagonal Number Theorem is represented by the entries A001318, A195310, A175003 and A000041. It seems unusual that the partition numbers are located in a middle column (see below row 1 of the table):
========================================================
. Column k of
. this square
. Generalized Triangle Triangle array A211970
k m m-gonal "A" "B" [row sums of
. numbers triangle "B"
. (if k>=1) with a(0)=1,
. if k >= 0]
========================================================
...
It appears that column 2 of the square array is A006950.
It appears that column 3 of the square array is A036820.
The partial sums of column 0 give A015128. - Omar E. Pol, Feb 09 2014

Examples

			Array begins:
1,     1,   1,   1,   1,   1,  1,  1,  1,  1,  1, ...
1,     1,   1,   1,   1,   1,  1,  1,  1,  1,  1, ...
2,     2,   1,   1,   1,   1,  1,  1,  1,  1,  1, ...
4,     3,   2,   1,   1,   1,  1,  1,  1,  1,  1, ...
6,     5,   3,   2,   1,   1,  1,  1,  1,  1,  1, ...
10,    7,   4,   3,   2,   1,  1,  1,  1,  1,  1, ...
16,   11,   5,   4,   3,   2,  1,  1,  1,  1,  1, ...
24,   15,   7,   4,   4,   3,  2,  1,  1,  1,  1, ...
36,   22,  10,   5,   4,   4,  3,  2,  1,  1,  1, ...
54,   30,  13,   7,   4,   4,  4,  3,  2,  1,  1, ...
78,   42,  16,  10,   5,   4,  4,  4,  3,  2,  1, ...
112,  56,  21,  12,   7,   4,  4,  4,  4,  3,  2, ...
160,  77,  28,  14,  10,   5,  4,  4,  4,  4,  3, ...
224, 101,  35,  16,  12,   7,  4,  4,  4,  4,  4, ...
312, 135,  43,  21,  13,  10,  5,  4,  4,  4,  4, ...
432, 176,  55,  27,  14,  12,  7,  4,  4,  4,  4, ...
...
		

Crossrefs

For another version see A195825.

Formula

T(n,k) = A211971(n), if k = 0.
T(n,k) = A195825(n,k), if k >= 1.

A195826 Triangle read by rows with T(n,k) = n - A000217(k), n>=1, k>=1, if (n - A000217(k))>=0.

Original entry on oeis.org

0, 1, 2, 0, 3, 1, 4, 2, 5, 3, 0, 6, 4, 1, 7, 5, 2, 8, 6, 3, 9, 7, 4, 0, 10, 8, 5, 1, 11, 9, 6, 2, 12, 10, 7, 3, 13, 11, 8, 4, 14, 12, 9, 5, 0, 15, 13, 10, 6, 1, 16, 14, 11, 7, 2, 17, 15, 12, 8, 3, 18, 16, 13, 9, 4, 19, 17, 14, 10, 5, 20, 18, 15, 11, 6, 0
Offset: 1

Views

Author

Omar E. Pol, Sep 24 2011

Keywords

Comments

Also triangle read by rows in which column k lists the nonnegative integers A001477 starting at the row A000217(k).
This sequence is related to the generalized hexagonal numbers (A000217), A195836 and A006950 in the same way as A195310 is related to the generalized pentagonal numbers A001318, A175003 and A000041. See comments in A195825.

Examples

			Written as a triangle:
.  0;
.  1;
.  2,  0;
.  3,  1;
.  4,  2;
.  5,  3,  0;
.  6,  4,  1;
.  7,  5,  2;
.  8,  6,  3;
.  9,  7,  4,  0;
. 10,  8,  5,  1;
. 11,  9,  6,  2;
. 12, 10,  7,  3;
. 13, 11,  8,  4;
. 14, 12,  9,  5,  0;
. 15, 13,  10, 6,  1;
. 16, 14,  11, 7,  2;
. 17, 15,  12, 8,  3;
		

Crossrefs

A195852 Column 8 of array A195825. Also column 1 of triangle A195842. Also 1 together with the row sums of triangle A195842.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 4, 4, 4, 4, 4, 4, 5, 7, 10, 12, 13, 13, 13, 13, 13, 14, 16, 21, 27, 32, 34, 35, 35, 35, 36, 38, 44, 54, 67, 77, 83, 85, 86, 87, 89, 95, 107, 128, 152, 173, 185, 191, 194, 197, 203, 216, 242, 281, 328, 367, 393, 407
Offset: 0

Views

Author

Omar E. Pol, Oct 07 2011

Keywords

Comments

Note that this sequence contains four plateaus: [1, 1, 1, 1, 1, 1, 1, 1, 1], [4, 4, 4, 4, 4, 4, 4], [13, 13, 13, 13, 13], [35, 35, 35]. For more information see A210843 and other sequences of this family. - Omar E. Pol, Jun 29 2012
Number of partitions of n into parts congruent to 0, 1 or 9 (mod 10). - Peter Bala, Dec 10 2020

Crossrefs

Formula

G.f.: Product_{k>=1} 1/((1 - x^(10*k))*(1 - x^(10*k-1))*(1 - x^(10*k-9))). - Ilya Gutkovskiy, Aug 13 2017
a(n) ~ exp(Pi*sqrt(n/5))/(2*(sqrt(5)-1)*n). - Vaclav Kotesovec, Aug 14 2017
a(n) = a(n-1) + a(n-9) - a(n-12) - a(n-28) + + - - (with the convention a(n) = 0 for negative n), where 1, 9, 12, 28, ... is the sequence of generalized 12-gonal numbers A195162. - Peter Bala, Dec 10 2020

Extensions

More terms from Omar E. Pol, Jun 10 2012

A106459 Expansion of f(-x, -x^3) in powers of x where f(,) is Ramanujan's general theta function.

Original entry on oeis.org

1, -1, 0, -1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
Offset: 0

Views

Author

Michael Somos, May 02 2005

Keywords

Comments

Ramanujan theta functions: f(q) (see A121373), phi(q) (A000122), psi(q) (A010054), chi(q) (A000700).
This is a expansion of Ramanujan's general theta function in powers of x because |a(n)| = A010054(n) is also the characteristic function of generalized hexagonal numbers. - Omar E. Pol, Jun 13 2012
Number 4 of the 14 primitive eta-products which are holomorphic modular forms of weight 1/2 listed by D. Zagier on page 30 of "The 1-2-3 of Modular Forms". - Michael Somos, May 04 2016
Also the number of partitions of n into an even number of parts, where each part occurs at most 3 times, minus the number of partitions of n into an odd number of parts, where each part occurs at most 3 times. - Jeremy Lovejoy, Aug 04 2020

Examples

			G.f. = 1 - x - x^3 + x^6 + x^10 - x^15 - x^21 + x^28 + x^36 - x^45 - x^55 + x^66 + ...
G.f. = q - q^9 - q^25 + q^49 + q^81 - q^121 - q^169 + q^225 + q^289 - q^361 - ...
		

References

  • D. M. Bressoud, Proofs and Confirmations, Camb. Univ. Press, 1999; p. 53, Exer. 2.2.10

Crossrefs

Programs

  • Mathematica
    a[ n_] := If[ SquaresR[ 1, 8 n + 1] == 2, (-1)^Quotient[ Sqrt[8 n + 1] + 1, 4], 0]; (* Michael Somos, Nov 18 2011 *)
    a[ n_] := SeriesCoefficient[ EllipticTheta[ 2, Pi/4, q] / (2^(1/2) q^(1/4)), {q, 0, 2 n}]; (* Michael Somos, Nov 18 2011 *)
  • PARI
    {a(n) = my(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x + A) * eta(x^4 + A) / eta(x^2 + A), n))}
    
  • PARI
    {a(n) = my(x); if( issquare( 8*n + 1, &x), kronecker( 2, x))};

Formula

Expansion of psi(-x) = f(x^6, x^10) - x * f(x^2, x^14) in powers of x where psi() is a Ramanujan theta function, and f(,) is Ramanujan's general theta function.
Expansion of q^(-1/8) * eta(q) * eta(q^4) / eta(q^2) in powers of q.
Euler transform of period 4 sequence [ -1, 0, -1, -1, ...].
G.f. is a period 1 Fourier series which satisfies f(-1 / (256 t)) = 4 (t/i)^(1/2) f(t) where q = exp(2 Pi i t).
Given g.f. A(x), then B(q) = q * A(q^8) satisfies 0 = f(B(q), B(q^2), B(q^3), B(q^6)) where f(u1, u2, u3, u6) = u1^4*u6^4 + u1^3*u2*u3^3*u6 + 2*u1*u2^3*u3*u6^3 - u2^4*u3^4.
a(n) = b(8*n + 1) where b() is multiplicative with b(p^e) = Kronecker(2, p)^(e/2) if e even, b(p^e) = 0 if e odd.
G.f.: Product_{k>0} (1 - x^k) * (1 + x^(2*k)) = Product_{k>0} (1 - x^k) / (1 - x^(4*k - 2)).
G.f.: Product_{k>0} (1 - x^(2*k)) / (1 + x^(2*k - 1)) = Product_{k>0} (1 - x^(4*k)) * (1 - x^(2*k - 1)).
G.f.: Sum_{k>=0} a(k) * x^(8*k + 1) = Sum_{k in Z} (-1)^k * x^((4*k + 1)^2).
G.f.: Sum_{k>=0} (-x)^(k*(k + 1)/2) = Sum_{k in Z} x^(8*k^2 + 2*k) - x^(8*k^2 + 6*k + 1).
G.f. A(x) satisfies: x / A(F(x)) = F(x) = g.f. of A192540.
Convolution inverse of A006950.
|a(n)| = A010054(n) the characteristic function of triangular numbers.
G.f.: 1 + (-x)*(1 + (-x)^2*(1 + (-x)^3*(1 + ...))). - Michael Somos, Mar 03 2014

A061563 Start with n; add to itself with digits reversed; if palindrome, stop; otherwise repeat; a(n) gives palindrome at which it stops, or -1 if no palindrome is ever reached.

Original entry on oeis.org

0, 2, 4, 6, 8, 11, 33, 55, 77, 99, 11, 22, 33, 44, 55, 66, 77, 88, 99, 121, 22, 33, 44, 55, 66, 77, 88, 99, 121, 121, 33, 44, 55, 66, 77, 88, 99, 121, 121, 363, 44, 55, 66, 77, 88, 99, 121, 121, 363, 484, 55, 66, 77, 88, 99, 121, 121, 363, 484, 1111, 66, 77, 88, 99, 121
Offset: 0

Views

Author

N. J. A. Sloane, May 18 2001

Keywords

Comments

It is believed that n = 196 is the smallest integer which never reaches a palindrome.

Examples

			19 -> 19 + 91 = 110 -> 110 + 011 = 121, so a(19) = 121.
		

Crossrefs

Cf. A033865. A016016 (number of steps), A023109, A006950, A023108.

Programs

  • ARIBAS
    var st: stack; test: boolean; end; for k := 0 to 60 do n := k; test := true; while test do n := n + int_reverse(n); test := n <> int_reverse(n); end; stack_push(st,n); end; stack2array(st);
  • Mathematica
    tol = 1000; r[n_] := FromDigits[Reverse[IntegerDigits[n]]]; palQ[n_] := n == r[n]; ar[n_] := n + r[n]; Table[k = 0; If[palQ[n], n = ar[n]; k = 1]; While[! palQ[n] && k < tol, n = ar[n]; k++]; If[k == tol, n = -1]; n, {n, 0, 64}] (* Jayanta Basu, Jul 11 2013 *)
    Table[Module[{k=n+IntegerReverse[n]},While[k!=IntegerReverse[k],k=k+IntegerReverse[k]];k],{n,0,70}] (* The program uses the IntegerReverse function from Mathematica version 10 *) (* Harvey P. Dale, Jul 19 2016 *)

Extensions

Corrected and extended by Klaus Brockhaus, May 20 2001
More terms from Ray Chandler, Jul 25 2003

A102759 Number of partitions of n-set in which number of blocks of size 2k is even (or zero) for every k.

Original entry on oeis.org

1, 1, 1, 2, 8, 27, 82, 338, 1647, 7668, 37779, 210520, 1276662, 7985200, 51302500, 358798144, 2677814900, 20309850311, 160547934756, 1344197852830, 11666610870142, 104156661915427, 962681713955130, 9238216839975106, 91508384728188792, 930538977116673878
Offset: 0

Views

Author

Vladeta Jovovic, Feb 10 2005, Aug 05 2007

Keywords

Crossrefs

Programs

  • Maple
    with(combinat):
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
           add(`if`(irem(i, 2)=1 or irem(j, 2)=0, multinomial(
           n, n-i*j, i$j)/j!*b(n-i*j, i-1), 0), j=0..n/i)))
        end:
    a:= n-> b(n$2):
    seq(a(n), n=0..30);  # Alois P. Heinz, Mar 08 2015
  • Mathematica
    multinomial[n_, k_List] := n!/Times @@ (k!); b[n_, i_] := b[n, i] = If[n == 0, 1, If[i<1, 0, Sum[If[Mod[i, 2] == 1 || Mod[j, 2] == 0, multinomial[n, Join[{n-i*j}, Table[i, {j}]]]/j!*b[n-i*j, i-1], 0], {j, 0, n/i}]]] ; a[n_] := b[n, n]; Table[ a[n], {n, 0, 30}] (* Jean-François Alcover, Mar 16 2015, after Alois P. Heinz *)
  • PARI
    N=31; x='x+O('x^N);
    Vec(serlaplace(exp(sinh(x))*prod(k=1,N,cosh(x^(2*k)/(2*k)!))))
    /* gives: [1, 1, 1, 2, 8, 27, 82, 338, 1647, 7668, ...] , Joerg Arndt, Jan 03 2011 */

Formula

E.g.f. for offset 2: exp(sinh(x))*Product_{k>=1} cosh(x^(2*k)/(2*k)!). - Geoffrey Critzer, Jan 02 2011

Extensions

Offset changed to 0 and two 1's prepended by Alois P. Heinz, Mar 08 2015

A131942 Number of partitions of n in which each odd part has odd multiplicity.

Original entry on oeis.org

1, 1, 1, 3, 3, 6, 6, 11, 13, 21, 24, 35, 44, 59, 74, 99, 126, 158, 202, 250, 320, 392, 495, 598, 758, 908, 1134, 1358, 1685, 2003, 2466, 2925, 3576, 4234, 5129, 6064, 7308, 8612, 10305, 12135, 14443, 16963, 20085, 23548, 27754, 32482, 38105, 44503, 52042
Offset: 0

Views

Author

Brian Drake, Jul 30 2007

Keywords

Examples

			a(5)=6 because 5, 4+1, 3+2, 2+2+1, 2+1+1+1 and 1+1+1+1+1 have all odd parts with odd multiplicity. The partition 3+1+1 is the partition of 5 which is not counted.
		

Crossrefs

Programs

  • Maple
    A:= series(product( 1/(1-q^(2*n)) *(1+q^(2*n-1)-q^(4*n-2))/(1-q^(4*n-2)), n=1..15),q,25): seq(coeff(A,q,i), i=0..24);
  • Mathematica
    nmax = 50; CoefficientList[Series[Product[(1 + x^(2*k-1) - x^(4*k-2))/ ((1-x^(2*k)) * (1-x^(4*k-2))), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Jan 03 2016 *)

Formula

G.f.: Product_{n>=1} (1+q^(2n-1)-q^(4n-2))/((1-q^(2n))(1-q^(4n-2))).
a(n) ~ sqrt(Pi^2 + 8*log(phi)^2) * exp(sqrt((Pi^2 + 8*log(phi)^2)*n/2)) / (8*Pi*n), where phi = A001622 = (1+sqrt(5))/2 is the golden ratio. - Vaclav Kotesovec, Jan 03 2016

A014670 G.f.: (1+x)*(1+x^3)*(1+x^5)*(1+x^7)*(1+x^9)/((1-x^2)*(1-x^4)*(1-x^6)*(1-x^8)*(1-x^10)).

Original entry on oeis.org

1, 1, 1, 2, 3, 4, 5, 7, 10, 13, 16, 20, 26, 32, 38, 47, 58, 69, 81, 96, 114, 133, 153, 177, 206, 236, 267, 304, 346, 390, 437, 490, 550, 613, 679, 753, 835, 921, 1011, 1111, 1221, 1335, 1455, 1586, 1728, 1877, 2032, 2200, 2382, 2571, 2768, 2980, 3207, 3443, 3689, 3952
Offset: 0

Views

Author

N. J. A. Sloane, Dec 31 2003

Keywords

Comments

Poincaré series [or Poincare series] (or Molien series) for symmetric invariants in F_2(b_1, b_2, ... b_n) ⊗ E(e_1, e_2, ... e_n) with b_i 2-dimensional, e_i one-dimensional and the permutation action of S_n, in the case n=5.

References

  • A. Adem and R. J. Milgram, Cohomology of Finite Groups, Springer-Verlag, 2nd. ed., 2004; p. 108.

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[(1+x)*(1+x^3)*(1+x^5)*(1+x^7)*(1+x^9)/((1-x^2)*(1-x^4)*(1-x^6)*(1-x^8)*(1-x^10)), {x, 0, 50}], x] (* Jinyuan Wang, Mar 10 2020 *)
    LinearRecurrence[{3,-5,8,-11,14,-18,21,-23,24,-24,23,-21,18,-14,11,-8,5,-3,1},{1,1,1,2,3,4,5,7,10,13,16,20,26,32,38,47,58,69,81},60] (* Harvey P. Dale, Mar 28 2023 *)
  • PARI
    Vec((1+x)*(1+x^3)*(1+x^5)*(1+x^7)*(1+x^9)/((1-x^2)*(1-x^4)*(1-x^6)*(1-x^8)*(1-x^10))+ O(x^100)) \\ Michel Marcus, Mar 18 2014

Formula

G.f.: -(x^2-x+1) *(x^6-x^5+x^4-x^3+x^2-x+1) *(x^6-x^3+1) / ( (x^4+x^3+x^2+x+1) *(1+x+x^2) *(x^4+1) *(x^2+1)^2 *(x-1)^5 ). - R. J. Mathar, Dec 18 2014
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