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 A108537 Concatenation of palindrome k and its 10's complement is prime. 1
 1, 3, 7, 77, 99, 151, 161, 333, 707, 727, 737, 757, 949, 969, 989, 1441, 1551, 1771, 1881, 3003, 7227, 7667, 7997, 9009, 9339, 9999, 10001, 10101, 10701, 11111, 11611, 11711, 12221, 12921, 13231, 14341, 14841, 14941, 15851, 16661, 16961, 17071 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Contains 10^k-1 for k in A056696, and (10^k-1)/9 for k in A108966. - Robert Israel, Jan 22 2019 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE a(7)=161 because 1000-161 = 839 and 161839 is prime. MAPLE N:= 5: # for terms of <= N digits digrev:= proc(n) local L, i; L:= convert(n, base, 10); add(L[-i]*10^(i-1), i=1..nops(L)) end proc: Res:= 1, 3, 7, 9: for d from 2 to N do if d::even then m:= d/2; Res:= Res, seq(seq((i*10^(m-1)+j)*10^m + digrev(i*10^(m-1)+j), j=0..10^(m-1)-1), i=[1, 3, 7, 9]); else m:= (d-1)/2; Res:= Res, seq(seq(seq((i*10^(m-1)+j)*10^(m+1)+y*10^m+digrev(i*10^(m-1)+j), y=0..9), j=0..10^(m-1)-1), i=[1, 3, 7, 9]); fi od: filter:= proc(t) local r; r:= 10^(ilog10(t)+1)-t; isprime(t*10^(ilog10(r)+1)+r) end proc: select(filter, [Res]); # Robert Israel, Jan 22 2019 CROSSREFS Cf. A056696, A108966. Sequence in context: A234536 A103737 A354480 * A364660 A219292 A181554 Adjacent sequences: A108534 A108535 A108536 * A108538 A108539 A108540 KEYWORD base,easy,nonn AUTHOR Jason Earls, Jul 25 2005 STATUS approved

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Last modified December 1 03:32 EST 2023. Contains 367468 sequences. (Running on oeis4.)