Empirical: a(n) = -a(n-2) +a(n-3) +2*a(n-5) +a(n-6) +2*a(n-7) +a(n-8) -a(n-10) -3*a(n-11) -2*a(n-12) -4*a(n-13) -a(n-14) -2*a(n-15) +2*a(n-16) +a(n-17) +4*a(n-18) +2*a(n-19) +3*a(n-20) +a(n-21) -a(n-23) -2*a(n-24) -a(n-25) -2*a(n-26) -a(n-28) +a(n-29) +a(n-31)
Also a quartic polynomial plus a linear quasipolynomial with period 840, the first 12 being:
Empirical for n mod 840 = 0: a(n) = (15/2)*n^4 + (701/9)*n^3 - (23846/105)*n^2 - (1769/35)*n + 1
Empirical for n mod 840 = 1: a(n) = (15/2)*n^4 + (701/9)*n^3 - (23846/105)*n^2 - (1664/35)*n + (133093/630)
Empirical for n mod 840 = 2: a(n) = (15/2)*n^4 + (701/9)*n^3 - (23846/105)*n^2 - (10907/105)*n + (175159/315)
Empirical for n mod 840 = 3: a(n) = (15/2)*n^4 + (701/9)*n^3 - (23846/105)*n^2 - (2084/35)*n + (7001/14)
Empirical for n mod 840 = 4: a(n) = (15/2)*n^4 + (701/9)*n^3 - (23846/105)*n^2 - (1769/35)*n + (73067/315)
Empirical for n mod 840 = 5: a(n) = (15/2)*n^4 + (701/9)*n^3 - (23846/105)*n^2 - (10592/105)*n + (2311/18)
Empirical for n mod 840 = 6: a(n) = (15/2)*n^4 + (701/9)*n^3 - (23846/105)*n^2 - (1769/35)*n - (4969/35)
Empirical for n mod 840 = 7: a(n) = (15/2)*n^4 + (701/9)*n^3 - (23846/105)*n^2 - (2084/35)*n + (30739/90)
Empirical for n mod 840 = 8: a(n) = (15/2)*n^4 + (701/9)*n^3 - (23846/105)*n^2 - (10907/105)*n + (27191/63)
Empirical for n mod 840 = 9: a(n) = (15/2)*n^4 + (701/9)*n^3 - (23846/105)*n^2 - (1664/35)*n + (10141/70)
Empirical for n mod 840 = 10: a(n) = (15/2)*n^4 + (701/9)*n^3 - (23846/105)*n^2 - (1769/35)*n + (20035/63)
Empirical for n mod 840 = 11: a(n) = (15/2)*n^4 + (701/9)*n^3 - (23846/105)*n^2 - (11852/105)*n + (367733/630)
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