

A243160


Least number k such that k^n  k^(n1) + k^(n2)  ... + (1)^n is prime or 0 if no such k exists.


0



3, 2, 2, 2, 0, 2, 0, 0, 0, 2, 0, 2, 0, 0, 0, 2, 0, 2, 0, 0, 0, 2, 0, 0, 0, 0, 0, 7, 0, 2, 0, 0, 0, 0, 0, 16, 0, 0, 0, 61, 0, 2, 0, 0, 0, 6, 0, 0, 0, 0, 0, 10, 0, 0, 0, 0, 0, 6, 0, 2, 0, 0, 0, 0, 0, 5, 0, 0, 0, 46, 0, 18, 0, 0, 0, 0, 0, 2, 0, 0, 0, 49, 0, 0, 0, 0, 0, 16, 0, 0, 0, 0, 0, 0, 0, 70
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OFFSET

1,1


COMMENTS

If n is in A006093, then a(n) is not 0.
The only term where the converse is false is a(3) = 2. Also, 2 is the only such number that makes k^3  k^2 + k  1 prime. Otherwise, a(n) is not 0 iff n is in A006093.


LINKS

Table of n, a(n) for n=1..96.


EXAMPLE

1^4  1^3 + 1^2  1^1 + 1 = 1 is not prime. 2^4  2^3 + 2^2  2^1 + 1 = 11 is prime. Thus a(4) = 2.


PROG

(PARI) a(n)=for(k=1, 1000, s=k^n; if(ispseudoprime(s+sum(i=1, n, (1)^i*k^(ni))), return(k)))
n=1; while(n<100, print1(a(n), ", "); n+=1)


CROSSREFS

Cf. A006093.
Sequence in context: A071048 A098054 A075801 * A272694 A292370 A116943
Adjacent sequences: A243157 A243158 A243159 * A243161 A243162 A243163


KEYWORD

nonn


AUTHOR

Derek Orr, May 31 2014


STATUS

approved



