A152652 Least prime p with digit sum A047235(n).

2, 13, 17, 19, 59, 79, 389, 499, 1889, 1999, 6899, 17989, 39989, 49999, 98999, 199999, 599999, 799999, 2999999, 4999999, 9899999, 19999999, 59999999, 189997999, 389999999, 689899999, 998999999, 2999899999, 6999999989, 9899989999, 39899999999, 68899999999, 98999999999

Offset: 1

Author

Giovanni Teofilatto, Dec 10 2008

Keywords

• nonn
• base

Links

• David A. Corneth, Table of n, a(n) for n = 1..1713

Crossrefs

Cf. A111380 (smallest prime whose digital sum is equal to the n-th composite number not congruent to 0 (modulo 3)). - Klaus Brockhaus, Dec 12 2008

Cf. A000040, A007605, A047234, A047235.

Programs

Magma

T:=[ n eq 1 select 2 else Self(n-1)+2*(1+n mod 2): n in [1..22] ]; S:=[]; p:=2; for k in T do while &+Intseq(p, 10) ne k do p:=NextPrime(p); end while; Append(~S,p); end for; S; // Klaus Brockhaus, Dec 13 2008

PARI

a(n) = {n = (n-1)\2*6+3+(-1)^n ; t = ceil(n/9); leastfound = oo; while(leastfound == oo, my(p = partitions(n, [1,9], [t,t])); v = vector(#p, i, oo); for(i = 1, #p, if(fromdigits(Vec(p[i])) > leastfound, next(2)); forperm(Vec(p[i]), q, if(isprime(fromdigits(Vec(q))), leastfound = min(leastfound, fromdigits(Vec(q))); v[i] = min(v[i], fromdigits(Vec(q))); next(2); ) ) ); t++ ); leastfound }\\ David A. Corneth, Jun 13 2020

Formula

{min A000040(i): A007605(i) = A047234(n)}. - R. J. Mathar, Dec 12 2008

Extensions

Edited and extended by R. J. Mathar, Dec 12 2008

a(20)-a(22) from Klaus Brockhaus, Dec 13 2008

More terms from Jinyuan Wang, Jun 13 2020