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A274173
Numbers n such that n is not divisible by 5 and n^k is of the form a^2 + b^4 for all k not divisible by 4.
0
609076, 9745216, 28998521, 36924641
OFFSET
1,1
COMMENTS
Numbers n such that n, n^2 and n^3 is in A111925 and n is not divisible by 5.
Since there cannot be fourth power in A111925, this sequence focuses on the values of k that is not divisible by 4 in definition.
EXAMPLE
609076 is a term because 609076 = 710^2 + 18^4, 609076^2 = 581940^2 + 424^4, 609076^3 = 475342920^2 + 676^4 and it is not divisible by 5.
PROG
(PARI) isA111925(n) = for(b=1, sqrtnint(n-1, 4), if(issquare(n-b^4), return(1))); 0;
isok(n) = n%5 != 0 && isA111925(n) && isA111925(n^2) && isA111925(n^3);
CROSSREFS
Cf. A111925.
Sequence in context: A351721 A340924 A218107 * A206175 A205429 A308279
KEYWORD
nonn,more
AUTHOR
Altug Alkan, Jun 12 2016
STATUS
approved