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A081227 a(n) is the number of digits in common between n and the n-th prime in base 10. 2


%S 0,0,0,0,0,0,1,0,0,0,1,0,1,1,0,0,0,1,0,0,0,0,1,0,0,0,0,0,1,1,1,1,1,1,

%T 0,0,1,1,0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,1,1,1,0,0,0,0,0,1,1,0,0,0,0,0,

%U 0,0,0,0,2,1,1,0,0,1,0,1,1,1,1,1,0,0,0,0,0,0,0,1,0,2,1,0,1,0,0,1,0,0,1,0,2

%N a(n) is the number of digits in common between n and the n-th prime in base 10.

%C Duplicate digits are ignored for comparison purposes; e.g. 1002 and 3050 only have one digit in common, 0.

%e a(7)=1 since the 7th prime is 17.

%p digcomp := proc(A,B) local a,b,crit,f; description "returns the digits that 'A' and 'B' have in common; if a third argument is given and it is 'sum' then the sum of the common digits is returned, else if it is 'num' then the number of common digits is returned."; if nargs>2 then crit := args[3] else crit := NULL fi; a := convert(`if`(A=0,[0],(convert(A,base,10))),set); b := convert(`if`(B=0,[0],(convert(B,base,10))),set); f := a intersect b; if crit=sum then return `if`(nops(f)>0,`+`(op(f)),-1) elif crit=num then return nops(f) else return f; fi; end proc;

%Y Cf. A081228, A081229.

%K base,easy,nonn

%O 1,73

%A Francois Jooste (pin(AT)myway.com), Mar 11 2003

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Last modified May 26 17:16 EDT 2022. Contains 354092 sequences. (Running on oeis4.)