all-base composites

[Tanya Khovanova]

Hello seqfans,

I recently submitted a sequence I really like. I am also suggesting a name for it: all-base composites.

I am not sure how to code this sequence. Can you help?


A121719  Strings of digits which are composite regardless of the base in which they are interpreted. Exclude bases in which numbers are not interpretable. 
 
 4, 6, 8, 9, 20, 22, 24, 26, 28, 30, 33, 36, 39, 40, 42, 44, 46, 48, 50, 55, 60, 62, 63, 64, 66, 68, 69, 70, 77, 80, 82, 84, 86, 88, 90, 93, 96, 99, 100
  
 EXAMPLE  String 55 in every base in which it is interpretable is divisible by 5. String 1001 in base a is divisible by a+1. Hence 55 and 1001 both belong to this sequence. 
 
 



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