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.

Previous Showing 11-14 of 14 results.

A385688 E.g.f. A(x) satisfies A(x) = exp( x*((A(x) + A(-x))/2)^3 ).

Original entry on oeis.org

1, 1, 1, 10, 37, 736, 4861, 145552, 1392553, 55772416, 700205401, 35139710464, 546584937229, 32977620613120, 612127803448981, 43150087404292096, 930914421449463505, 75083676142358560768, 1846230024226716759601, 167681514857730519728128, 4629062510444281987051381
Offset: 0

Views

Author

Seiichi Manyama, Jul 06 2025

Keywords

Crossrefs

Programs

  • Mathematica
    terms = 21; A[] = 1; Do[A[x] = Exp[x*((A[x] + A[-x])/2)^3] + O[x]^terms // Normal, terms]; CoefficientList[A[x], x]Range[0,terms-1]! (* Stefano Spezia, Jul 07 2025 *)

Formula

E.g.f. A(x) satisfies A(-x) = 1/A(x).
a(0) = 1; a(n) = (n-1)! * Sum_{i, j, k, l>=0 and i+2*j+2*k+2*l=n-1} (n-i) * a(i) * a(2*j) * a(2*k) * a(2*l)/(i! * (2*j)! * (2*k)! * (2*l)!).

A385725 E.g.f. A(x) satisfies A(x) = exp( x*(A(x) + A(i*x) + A(-x) + A(-i*x))/4 ), where i is the imaginary unit.

Original entry on oeis.org

1, 1, 1, 1, 1, 6, 31, 106, 281, 3160, 29701, 176056, 768241, 12702704, 173361371, 1466276176, 8937060081, 195180709248, 3494232292681, 38426220716416, 301057954180801, 8174141246647552, 181144607099402871, 2452803139819922176, 23494461553739152201, 762800754226165963776
Offset: 0

Views

Author

Seiichi Manyama, Jul 08 2025

Keywords

Crossrefs

Formula

a(0) = 1; a(n) = Sum_{k=0..floor((n-1)/4)} (4*k+1) * binomial(n-1,4*k) * a(4*k) * a(n-1-4*k).

A143598 E.g.f.: A(x) = exp(x*sinh(x*G(x))) where G(x) = cosh(x*G(x)) is the e.g.f. of A143601.

Original entry on oeis.org

1, 2, 28, 1176, 103440, 15726880, 3684098496, 1232799974784, 558670427013376, 329559835063067136, 245462725323910487040, 225319148634038399801344, 249936012383478860884217856, 329609037187846742271984869376
Offset: 0

Views

Author

Paul D. Hanna, Aug 27 2008

Keywords

Examples

			E.g.f.: A(x) = 1 + 2*x^2/2! + 28*x^4/4! + 1176*x^6/6! + 103440*x^8/8! +...
A(x) = exp(x*F(x)) where F(x) = e.g.f. of A007106:
F(x) = x + 4*x^3/3! + 96*x^5/5! + 5888*x^7/7! + 686080*x^9/9! +...
A(x) = exp(x*sqrt(G(x)^2 - 1)) where G(x) = e.g.f. of A143601:
G(x) = 1 + x^2/2! + 13*x^4/4! + 541*x^6/6! + 47545*x^8/8! +...
A(x) = sqrt(H(x)*H(-x)) where H(x) = e.g.f. of A143599:
H(x) = 1 + x + 3*x^2/2! + 10*x^3/3! + 53*x^4/4! + 316*x^5/5! +...
		

Crossrefs

Programs

  • PARI
    {a(n)=local(G=1+x*O(x^n));for(i=0,n,G=cosh(x*G));n!*polcoeff(exp(x*sqrt(G^2-1)),n)}

Formula

E.g.f.: A(x) = exp(x*F(x)) where F(x) is the e.g.f. of A007106.
E.g.f.: A(x) = sqrt(H(x)*H(-x)) where H(x) = exp(x*sqrt(H(x)/H(-x))) is the e.g.f. of A143599.
E.g.f. satisfies: A(x/cosh(x)) = exp(x*tanh(x)). [From Paul D. Hanna, Aug 29 2008]

A263547 E.g.f. satisfies: A(x) = exp( x * real( A(x)^I ) ), where I^2 = -1.

Original entry on oeis.org

1, 1, 1, -2, -11, 36, 421, -1896, -35223, 201232, 5188201, -35856160, -1188970595, 9633456704, 391498316301, -3636762088064, -175238714193967, 1835360835895552, 102369229796454481, -1193179646751072768, -75645902492063337659, 971018266973866894336, 68985480327663686993141, -966900537026209266460672
Offset: 0

Views

Author

Paul D. Hanna, Oct 20 2015

Keywords

Examples

			E.g.f.: A(x) = 1 + x + x^2/2! - 2*x^3/3! - 11*x^4/4! + 36*x^5/5! + 421*x^6/6! - 1896*x^7/7! - 35223*x^8/8! + 201232*x^9/9! + 5188201*x^10/10! +...
where
log(A(x)) = x - 3*x^3/3! + 65*x^5/5! - 3787*x^7/7! + 427905*x^9/9! - 79549811*x^11/11! +...+ A036778(n)*x^(2*n-1)/(2*n-1)! +...
which equals Series_Reversion( x/cos(x) ).
Also,
A(x)^I = 1 + I*x - x^2 - 4*I*x^3 + 13*x^4 + 96*I*x^5 - 541*x^6 - 5888*I*x^7/7! + 47545*x^8/8! +...+ A058014(n)*I^n*x^n/n! +...
Further,
Series_Reversion(A(x)-1) = log(1+x)/cos(log(1+x)) = e.g.f. of A009424.
		

Crossrefs

Programs

  • PARI
    {a(n) = my(A=1); for(i=1,n+1, A = exp(x*real(A^I) +x*O(x^n))); n!*polcoeff(A,n)}
    for(n=0,30,print1(a(n),", "))
    
  • PARI
    {a(n) = my(A=1); for(i=1,n+1, A = exp( serreverse( x/cos(x +x*O(x^n))))); n!*polcoeff(A,n)}
    for(n=0,30,print1(a(n),", "))

Formula

E.g.f.: A(x) = exp( Series_Reversion( x/cos(x) ) ).
Previous Showing 11-14 of 14 results.