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A144592 Composites of the form smallest digit of prime(n) + prime(n). 1
4, 6, 10, 14, 12, 14, 18, 20, 25, 32, 40, 42, 46, 51, 56, 64, 62, 72, 76, 86, 86, 104, 114, 128, 132, 138, 140, 150, 152, 158, 164, 168, 174, 180, 182, 192, 194, 198, 200, 212, 225, 231, 235, 242, 252, 259, 265, 272, 279, 282, 285, 295, 312, 314, 318, 332, 340, 350 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
23 is prime, 2 < 3, and 2 + 23 = 25 (composite) = a(9);
29 is prime, 2 < 9, and 2 + 29 = 31 (prime);
31 is prime, 3 > 1, and 1 + 31 = 32 (composite) = a(10); etc.
MAPLE
A054054 := proc(n) min(op(convert(n, base, 10)) ) ; end proc: A144592 := proc(n) p := ithprime(n) ; sd := A054054(p) ; if not isprime(p+sd) then printf("%d, ", p+sd) ; end if; end proc: seq(A144592(n), n=1..400) ; # R. J. Mathar, May 01 2010
MATHEMATICA
Select[#+Min[IntegerDigits[#]]&/@Prime[Range[100]], CompositeQ] (* Harvey P. Dale, Jun 28 2015 *)
PROG
(PARI) for(n=1, 1e3, if(isprime(k=if(n, vecmin(digits(prime(n)))) + prime(n)) == 0, print1(k", "))) \\ Altug Alkan, Oct 17 2015
CROSSREFS
Sequence in context: A302660 A255005 A137699 * A268185 A065073 A359157
KEYWORD
nonn,base
AUTHOR
EXTENSIONS
Sequence corrected (by adding 235, which had erroneously been omitted) by Harvey P. Dale, Feb 08 2009
STATUS
approved

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Last modified March 28 08:22 EDT 2024. Contains 371236 sequences. (Running on oeis4.)