OFFSET
0,6
COMMENTS
a(n) is the number of partitions of n into parts 2, 3, 5, and 7. - Joerg Arndt, Oct 01 2025
LINKS
Milan Janjic, On Linear Recurrence Equations Arising from Compositions of Positive Integers, Journal of Integer Sequences, Vol. 18 (2015), Article 15.4.7.
Index entries for linear recurrences with constant coefficients, signature (0,1,1,0,0,0,0,-1,-1,0,0,0,0,1,1,0,-1).
FORMULA
a(n) = floor((2*n^3+51*n^2+390*n+1960)/2520 - (n mod 2)/8 + ((n+2) mod 3)/9). - Hoang Xuan Thanh, Sep 30 2025
MATHEMATICA
CoefficientList[Series[1/((1-x^2)(1-x^3)(1-x^5)(1-x^7)), {x, 0, 60}], x] (* Harvey P. Dale, Oct 28 2011 *)
PROG
(Maxima) a(n):=floor((2*n^3+51*n^2+390*n+2020)/2520+((-1)^mod(n, 5)-floor(mod(n, 5)/4))/5); /* Tani Akinari, Nov 13 2012 */
(PARI) Vec(1/((1-x^2)*(1-x^3)*(1-x^5)*(1-x^7)) + O(x^90)) \\ Jinyuan Wang, Mar 18 2020
(PARI) a(n) = (2*n^3+51*n^2+390*n+1960 - 315*(n%2) + 280*((n+2)%3))\2520 \\ Hoang Xuan Thanh, Sep 30 2025
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved
