This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A074200 a(n) = m, the smallest number such that (m+k)/k is prime for k=1, 2, ..., n. 7
 1, 2, 12, 12720, 19440, 5516280, 5516280, 7321991040, 363500177040, 2394196081200, 3163427380990800, 22755817971366480, 3788978012188649280, 2918756139031688155200 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Computed by Jack Brennen and Phil Carmody. LINKS Walter Nissen, Calculation without Words : Doric Columns of Primes. C. Rivera, Puzzle 181 EXAMPLE (12+k)/k is prime for k = 1,2,3. 12 is the smallest such number so a(3) = 12. MATHEMATICA a[1] = 1; a[n_] := a[n] = For[dm = LCM @@ Range[n]; m = Quotient[a[n - 1], dm]*dm, True, m = m + dm, If[AllTrue[Range[n], PrimeQ[(m + #)/#] &], Return[m]]]; Table[an = a[n]; Print["a(", n, ") = ", an]; an, {n, 1, 10}] (* Jean-François Alcover, Dec 01 2016 *) PROG (PARI) isok(m, n) = {for (k = 1, n, if ((m+k) % k, return (0), if (! isprime((m+k)/k), return(0))); ); return (1); } a(n) = {m = 1; while(! isok(m, n), m++); m; } \\ Michel Marcus, Aug 31 2013 (Python) from sympy import isprime, lcm def A074200(n):     a = lcm(range(1, n+1))     m = a     while True:         for k in range(n, 0, -1):             if not isprime(m//k+1):                 break         else:             return m         m += a # Chai Wah Wu, Feb 27 2019 CROSSREFS Cf. A078502, A278500. One less than A093553. Sequence in context: A007155 A265092 A262032 * A274223 A280734 A048830 Adjacent sequences:  A074197 A074198 A074199 * A074201 A074202 A074203 KEYWORD nonn,more AUTHOR Jean-Christophe Colin (jc-colin(AT)wanadoo.fr), Sep 17 2002, May 10 2010 EXTENSIONS Corrected by Vladeta Jovovic, Jan 08 2003 a(14) from Jens Kruse Andersen, Feb 15 2004 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified April 19 20:04 EDT 2019. Contains 322291 sequences. (Running on oeis4.)