OFFSET
0,3
COMMENTS
Structured heptagonal prism numbers. - James A. Record (james.record(AT)gmail.com), Nov 07 2004
Apart from 0, partial sums of A220083. [Bruno Berselli, Dec 11 2012]
REFERENCES
W. A. Whitworth, DCC Exercises in Choice and Chance, Stechert, NY, 1945, p. 29.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..10000
Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).
FORMULA
a(n) = (1/6)*(15*n^3-9*n^2). - James A. Record (james.record(AT)gmail.com), Nov 07 2004
G.f.: x*(1+10*x+4*x^2)/(1-x)^4. - Colin Barker, Jun 08 2012
a(n) = Sum_{i=0..n-1} n*(5*i+1) for n>0. [Bruno Berselli, Sep 08 2015]
Sum_{n>=1} 1/a(n) = 1.1080093773051638036... = (sqrt(5*(5 - 2*sqrt(5)))*Pi - Pi^2 - 5*sqrt(5)*arccoth(sqrt(5)) + (25*log(5))/2)/9. - Vaclav Kotesovec, Oct 04 2016
MAPLE
MATHEMATICA
Table[n^2*(5*n-3)/2, {n, 0, 40}] (* Wesley Ivan Hurt, Mar 11 2014 *)
PROG
(Magma) [n^2*(5*n-3)/2: n in [0..40]]; // Vincenzo Librandi, Jul 20 2011
(PARI) a(n)=n^2*(5*n-3)/2; \\ Joerg Arndt, Jul 20 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Name corrected by Arkadiusz Wesolowski, Jul 20 2011
STATUS
approved