This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A049126 Revert transform of ((x - 1)(3x - 1))/(1 - 3x + x^3). 0
 1, 1, 2, 6, 22, 90, 393, 1789, 8378, 40050, 194492, 956448, 4752519, 23822571, 120315345, 611644737, 3127389106, 16072642890, 82981119252, 430187414196, 2238469102212, 11687227631892, 61208286479382, 321465732705594 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS FORMULA Revert transform of A122100 offset 1. - Michael Somos, May 11 2012 EXAMPLE G.f. = x + x^2 + 2*x^3 + 6*x^4 + 22*x^5 + 90*x^6 + 393*x^7 + 1789*x^8 + ... PROG (PARI) {a(n) = if( n<1, 0, polcoeff( serreverse(x * (1 - 4*x + 3*x^2) / (1 - 3*x + x^3) + x * O(x^n)), n))}; /* Michael Somos, May 11 2012 */ CROSSREFS Cf. A122100. Sequence in context: A150270 A049136 A165523 * A049134 A086456 A155069 Adjacent sequences:  A049123 A049124 A049125 * A049127 A049128 A049129 KEYWORD nonn AUTHOR STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 10 04:15 EST 2019. Contains 329885 sequences. (Running on oeis4.)