The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A154507 Nonprimes formed by concatenation of the decimal digits of a nonprime and its index. 0
 1, 12, 64, 85, 96, 128, 1510, 1611, 1812, 2013, 2114, 2215, 2416, 2517, 2618, 2820, 3021, 3222, 3424, 3525, 3626, 3827, 3928, 4029, 4230, 4431, 4532, 4633, 4834, 4935, 5036, 5137, 5238, 5439, 5540, 5742, 6044, 6245, 6346, 6447, 6548, 6649, 6850, 6951 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Nonprimes of the form A141468(k)//k, where double slashes represent concatenation, sorted along increasing k. LINKS Table of n, a(n) for n=1..44. EXAMPLE A141468(n=1)//1 = 0//1 = 1 is not prime and inserted into the sequence. A141468(n=2)//2 = 1//2 = 12 is not prime and inserted into the sequence. A141468(n=3)//3 = 4//3 = 43 is prime and not inserted into the sequence. MAPLE cat2 := proc(a, b) dgs := max(1, ilog10(b)+1) ; a*10^dgs+b ; end: n := 0 ; for c from 0 to 80 do if not isprime(c) then n := n + 1 ; if not isprime(cat2(c, n)) then printf("%d, ", cat2(c, n)) ; fi; fi; od: # R. J. Mathar, Aug 03 2009 CROSSREFS Cf. A000040, A141468. Sequence in context: A275404 A162472 A008425 * A105916 A193872 A258617 Adjacent sequences: A154504 A154505 A154506 * A154508 A154509 A154510 KEYWORD nonn,base AUTHOR Juri-Stepan Gerasimov, Jan 11 2009 EXTENSIONS Edited by R. J. Mathar, Aug 03 2009 STATUS approved

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

Last modified September 18 07:20 EDT 2024. Contains 375996 sequences. (Running on oeis4.)