A144591 - OEIS

%I #9 Nov 15 2015 08:19:10

%S 8,16,24,27,32,32,38,42,44,48,54,60,62,68,74,81,85,91,99,105,111,128,

%T 133,140,142,152,154,160,166,170,180,183,194,201,203,215,231,234,244,

%U 255,262,268,274,276,282,284,295,310,315,318,323,343,354,361,370,377

%N Composites of the form smallest digit of n + prime(n).

%e Prime(1) = 2 and 1 + 2 = 3 (prime);

%e prime(2) = 3 and 2 + 3 = 5 (prime);

%e prime(3) = 5 and 3 + 5 = 8 (composite), so a(1) = 8;

%e prime(4) = 7 and 4 + 7 = 11 (prime);

%e prime(5) = 11 and 5 + 11 = 16 (composite), so a(2) = 16; etc.

%p A054054 := proc(n) min(op(convert(n,base,10)) ) ; end proc: A144591 := proc(n) p := ithprime(n) ; sd := A054054(n) ; if not isprime(p+sd) then printf("%d,",p+sd) ; end if; end proc: seq(A144591(n),n=1..400) ; # _R. J. Mathar_, May 01 2010

%t Select[Table[Prime[n]+Min[IntegerDigits[n]],{n,80}],CompositeQ] (* The program uses the CompositeQ function from Mathematica version 10 *) (* _Harvey P. Dale_, Nov 15 2015 *)

%Y Cf. A000040, A002808.

%K nonn,base

%O 1,1

%A _Juri-Stepan Gerasimov_, Jan 12 2009

%E Corrected (369 replaced by 370) by _R. J. Mathar_, May 01 2010