A081952 Smallest Fibonacci number which is one more than the product of n distinct numbers > 1.
3, 13, 55, 1597, 17711, 1346269, 165580141, 2971215073, 7778742049, 308061521170129, 308061521170129, 135301852344706746049, 3311648143516982017180081, 1983924214061919432247806074196061
Offset: 1
Keywords
Examples
a(3) = 2*3*9 + 1 = 55; a(4) = 3*4*7*19 + 1 = 1597; a(5) = 2*5*7*11*23 + 1 = 17711; a(6) = 3*4*7*11*31*47 + 1 = 1346269; a(7) = 3*4*5*11*29*41*211 + 1 = 165580141; a(8) = 2*3*6*7*8*23*139*461 + 1 = 2971215073.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..56
Programs
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Mathematica
f[n_, m_, 0] := n == 1; f[n_, m_, d_] := (b = False; l = Select[Divisors[n], #>=m&]; For[i = 1, i <= Length[l], i++, k = l[[i]]; If[f[n / k, k + 1, d - 1], b = True; Break[]]]; b); Do[x = 3; While[ !f[Fibonacci[x] - 1, 2, y], x++ ]; Print[Fibonacci[x]], {y, 1, 50}] (* Ryan Propper, Jul 22 2006 *)
Formula
Extensions
More terms from R. J. Mathar, Apr 13 2006
More terms from Ryan Propper, Jul 22 2006
Edited by Jon E. Schoenfield, Nov 18 2018