

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
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OFFSET

1,2


COMMENTS

Nonprimes of the form A141468(k)//k, where double slashes represent concatenation, sorted along increasing k.


LINKS



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



KEYWORD

nonn,base


AUTHOR



EXTENSIONS



STATUS

approved



