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A282286
Least common multiple of 7*n+1 and 7*n-1.
3
1, 24, 195, 220, 783, 612, 1763, 1200, 3135, 1984, 4899, 2964, 7055, 4140, 9603, 5512, 12543, 7080, 15875, 8844, 19599, 10804, 23715, 12960, 28223, 15312, 33123, 17860, 38415, 20604, 44099, 23544, 50175, 26680, 56643, 30012, 63503, 33540, 70755, 37264, 78399
OFFSET
0,2
FORMULA
a(n) = 49*n^2-1 for n>0 and even.
a(n) = (49*n^2-1)/2 for n odd.
a(n) = 3*a(n-2) - 3*a(n-4) + a(n-6) for n>6.
G.f.: (1+24*x+192*x^2+148*x^3+201*x^4+24*x^5-2*x^6) / ((1-x)^3*(1+x)^3).
PROG
(PARI) vector(60, n, n--; lcm(7*n+1, 7*n-1))
(PARI) Vec((1+24*x+192*x^2+148*x^3+201*x^4+24*x^5-2*x^6) / ((1-x)^3*(1+x)^3) + O(x^60))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Feb 11 2017
STATUS
approved