A255642 a(n) = n*((n mod 3)*(n mod 5)-((n mod 3)+(n mod 5))).

0, -1, 0, -9, -4, -10, -6, -7, 8, -36, -10, -11, -24, -13, 28, 0, -16, 0, -54, -19, -40, -21, -22, 23, -96, -25, -26, -54, -28, 58, 0, -31, 0, -99, -34, -70, -36, -37, 38, -156, -40, -41, -84, -43, 88, 0, -46, 0, -144, -49, -100, -51, -52, 53, -216, -55, -56, -114, -58, 118, 0, -61, 0, -189, -64, -130, -66, -67, 68, -276, -70, -71, -144, -73, 148, 0

Offset: 0

Author

Zak Seidov, Mar 01 2015

Keywords

• sign
• easy

Comments

a(n) = 0 for n == {0,2} mod 15.

Links

• Colin Barker, Table of n, a(n) for n = 0..1000

Programs

Mathematica

Table[x*(Mod[x,3]*Mod[x,5]-(Mod[x,3]+Mod[x,5])),{x,0,100}]

PARI

vector(100, n, n*((n%3)*(n%5)-((n%3)+(n%5)))) \\ Colin Barker, Mar 01 2015

Formula

Empirical g.f. x*(2*x^20 -6*x^19 +6*x^17 -3*x^16 -14*x^15 +38*x^14 -46*x^13 +26*x^12 -16*x^11 -10*x^10 +48*x^9 -31*x^8 -4*x^7 -x^6 +8*x^5 -11*x^4 +14*x^3 -10*x^2 +2*x -1) / ((x -1)^2*(x^2 +x +1)^2*(x^8 -x^7 +x^5 -x^4 +x^3 -x +1)^2). - Colin Barker, Mar 01 2015