cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A277384 Least common multiple of n + 4 and n - 4.

Original entry on oeis.org

15, 6, 7, 0, 9, 10, 33, 12, 65, 42, 105, 16, 153, 90, 209, 60, 273, 154, 345, 48, 425, 234, 513, 140, 609, 330, 713, 96, 825, 442, 945, 252, 1073, 570, 1209, 160, 1353, 714, 1505, 396, 1665, 874, 1833, 240, 2009, 1050, 2193, 572, 2385, 1242, 2585, 336, 2793
Offset: 1

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Author

Colin Barker, Oct 12 2016

Keywords

Comments

The recurrence for the general case lcm(n+k, n-k) is b(n) = 3*b(n-2*k) - 3*b(n-4*k) + b(n-6*k) for n>6*k.

Crossrefs

Cf. A066830 (k=1), A249859 (k=2), A249860 (k=3).
Cf. A277385.

Programs

  • Maple
    A277384:=n->lcm(n+4,n-4): seq(A277384(n), n=1..100); # Wesley Ivan Hurt, Jul 09 2017
  • Mathematica
    Table[LCM[n + 4, n - 4], {n, 1, 25}] (* G. C. Greubel, Oct 12 2016 *)
  • PARI
    a(n) = lcm(n+4, n-4)
    
  • PARI
    Vec(x*(15 +6*x +7*x^2 +9*x^4 +10*x^5 +33*x^6 +12*x^7 +20*x^8 +24*x^9 +84*x^10 +16*x^11 +126*x^12 +60*x^13 +110*x^14 +24*x^15 +123*x^16 +46*x^17 +51*x^18 -7*x^20 -6*x^21 -15*x^22 -4*x^23 -30*x^24 -12*x^25 -14*x^26) / ((1 -x)^3*(1 +x)^3*(1 +x^2)^3*(1 +x^4)^3) + O(x^60))

Formula

a(n) = 3*a(n-8)-3*a(n-16)+a(n-24) for n>27.
G.f.: x*(15 +6*x +7*x^2 +9*x^4 +10*x^5 +33*x^6 +12*x^7 +20*x^8 +24*x^9 +84*x^10 +16*x^11 +126*x^12 +60*x^13 +110*x^14 +24*x^15 +123*x^16 +46*x^17 +51*x^18 -7*x^20 -6*x^21 -15*x^22 -4*x^23 -30*x^24 -12*x^25 -14*x^26) / ((1 -x)^3*(1 +x)^3*(1 +x^2)^3*(1 +x^4)^3).
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