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A034268
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Least common multiple of {2^k - 1, k=1..n}.
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4
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1, 3, 21, 105, 3255, 9765, 1240155, 21082635, 1539032355, 16929355905, 34654391537535, 450507089987955, 3690103574091339405, 158674453685927594415, 23959842506575066756665, 6157679524189792156462905, 807093212915080247739749421255
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| lcm(1, 3, 7, ..., 2^n - 1).
Product_{k=1..n} Phi_k(2), where Phi_n(2) is n-th cyclotomic polynomial at x=2(cf. A019320). - Vladeta Jovovic (vladeta(AT)eunet.rs), Jan 20 2002
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EXAMPLE
| a(3) = lcm(1,3,7) = 21.
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MAPLE
| a:= proc(n) option remember; `if`(n=1, 1, lcm(a(n-1), 2^n-1)) end:
seq (a(n), n=1..20); # Alois P. Heinz, Oct 16 2011
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PROG
| (PARI) A034268(n) = {local(r); r=1; for(k=1, n, r=lcm(r, 2^k-1)); r} [From Michael B. Porter, Mar 02 2010]
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CROSSREFS
| Cf. A051844.
Cf. A019320.
Sequence in context: A076207 A134057 A128281 * A140451 A054147 A043012
Adjacent sequences: A034265 A034266 A034267 * A034269 A034270 A034271
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KEYWORD
| nonn
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AUTHOR
| Jeffrey Shallit (shallit(AT)graceland.uwaterloo.ca), Apr 20 2000
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