A154513 The prime(n)-th digit of the concatenated composites.
6, 8, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 7, 7, 7, 8, 8, 9, 9, 9, 9, 1, 4, 6, 0, 1, 1, 1, 7, 1, 1, 1, 3, 8, 3, 1, 5, 1, 1, 1, 1, 1, 1, 1, 3, 5, 1, 8, 1, 8, 1, 0, 1, 7, 0, 1, 5, 1, 1, 2, 5, 8, 2, 2, 5, 2, 9, 2, 4, 2, 8, 0, 2, 2, 8, 2, 1, 2, 2, 2, 2, 6, 2, 2, 2, 5, 2, 5, 2, 2, 2, 5
Offset: 1
Programs
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Maple
a129808 := [1 ] : for n from 4 to 400 do if not isprime(n) then a129808 := [op(a129808), op(ListTools[Reverse](convert(n,base,10))) ] ; fi; od: for n from 1 do p := ithprime(n) ; printf("%d,", op(p+1,a129808) ) ; od: # R. J. Mathar, Aug 03 2009 -
Mathematica
nn=700;With[{c=Flatten[IntegerDigits/@Complement[Range[4,nn],Prime[Range[ PrimePi[nn]]]]]}, Flatten[Table[Take[c,{n,n}],{n,Prime[Range[ PrimePi[ nn]]]}]]] (* Harvey P. Dale, Nov 22 2013 *)
Formula
a(n) = A129808(prime(n)+1).
Extensions
Edited and corrected by R. J. Mathar, Aug 03 2009
Comments