A022269 a(n) = n*(11*n+1)/2.

0, 6, 23, 51, 90, 140, 201, 273, 356, 450, 555, 671, 798, 936, 1085, 1245, 1416, 1598, 1791, 1995, 2210, 2436, 2673, 2921, 3180, 3450, 3731, 4023, 4326, 4640, 4965, 5301, 5648, 6006, 6375, 6755, 7146, 7548, 7961, 8385, 8820, 9266, 9723, 10191, 10670, 11160

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Comments

Number of sets which can be obtained by selecting unique elements from two sets with 2n and 3n elements respectively and n common elements. - Dolmatov S. (aalma(AT)mail.ru), Jun 24 2003

Links

• G. C. Greubel, Table of n, a(n) for n = 0..5000
• Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

Crossrefs

Cf. A110449.

Cf. similar sequences listed in A022289.

Programs

Mathematica

Table[n*(11*n + 1)/2, {n,0,50}] (* G. C. Greubel, Aug 24 2017 *)

PARI

a(n)=n*(11*n+1)/2 \\ Charles R Greathouse IV, Jun 17 2017

Formula

a(n) = A110449(n, 5) for n>4.

a(n) = 11*n + a(n-1) - 5 with n>0, a(0)=0. - Vincenzo Librandi, Aug 04 2010

G.f.: x*(6 + 5*x)/(1 - x)^3. - Philippe Deléham, Mar 27 2013

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) with n>2, a(0)=0, a(1)=6, a(2)=23. - Philippe Deléham, Mar 27 2013

a(n) = A218530(11*n+5).

a(n) = A000217(6*n) - A000217(5*n). - Bruno Berselli, Oct 13 2016

E.g.f.: (x/2)*(11*x + 12)*exp(x). - G. C. Greubel, Aug 24 2017