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 A089754 Smallest prime ending (least significant side) in n if possible else beginning in n. 1
 11, 2, 3, 41, 5, 61, 7, 83, 19, 101, 11, 127, 13, 149, 151, 163, 17, 181, 19, 2003, 421, 223, 23, 241, 251, 263, 127, 281, 29, 307, 31, 3203, 233, 347, 353, 367, 37, 383, 139, 401, 41, 421, 43, 443, 457, 461, 47, 487, 149, 503, 151, 521, 53, 541, 557, 563, 157, 587, 59, 601, 61, 6203, 163 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS MAPLE read("transforms)"): nleadzero := proc(n, dgs)     local ndgs ;     if n = 0 then         ndgs := 0 ;     else         ndgs := ilog10(n)+1 ;     end if;     [op(convert(n, base, 10)), seq(0, i=1..dgs-ndgs)] end proc: digcatL2 := proc(L1, L2)     digcatL([op(L1), op(L2)]) ; end proc: A089754 := proc(n)     local prep, a, dgs ;     if isprime(n) then         n;     elif modp(n, 2) = 0 or modp(n, 5) = 0 then         ndgs := convert(n, base, 10) ;         for dgs from 1 do             for prep from 0 to 10^dgs-1 do                 a := digcatL2(ListTools[Reverse](ndgs), ListTools[Reverse](nleadzero(prep, dgs))) ;                 if isprime(a) then                     return a;                 end if;             end do:         end do:     else         for prep from 1 do             a := digcat2(prep, n) ;             if isprime(a) then                 return a;             end if;         end do:     end if; end proc: # R. J. Mathar, Sep 18 2015 CROSSREFS Cf. A018800, A062584, A068164. Sequence in context: A160137 A107698 A068164 * A110743 A077549 A089356 Adjacent sequences:  A089751 A089752 A089753 * A089755 A089756 A089757 KEYWORD base,easy,nonn AUTHOR Amarnath Murthy, Nov 22 2003 EXTENSIONS Corrected by R. J. Mathar, Sep 18 2015 STATUS approved

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Last modified August 9 22:52 EDT 2020. Contains 336335 sequences. (Running on oeis4.)