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A162930 Primes that can be written as a sum of a positive square and a positive cube in more than one way. 1
17, 89, 233, 449, 577, 593, 1289, 1367, 1601, 1753, 2089, 2521, 3391, 4481, 4721, 5953, 6121, 6427, 7057, 7577, 8081, 9649, 10313, 10657, 10729, 11969, 12329, 13121, 13457, 15137, 15193, 15641, 15661, 16033, 16649, 18523, 21673, 21961, 23201 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A subset of these, 2089, 4481, 7057, 15193, 15641, etc., allows this representation in more than two ways.

LINKS

Table of n, a(n) for n=1..39.

FORMULA

A000040 INTERSECT A054402.

EXAMPLE

The prime 17 can be written 1^3 + 4^2 as well as 2^3 + 3^2.

MAPLE

isA162930 := proc(n) if isprime(n) then wa := 0 ; for y from 1 to n/2 do if issqr(n-y^3) then if n -y^3 > 0 then wa := wa+1 ; fi; fi; od: RETURN( wa>1) ; else false; fi; end:

for i from 1 to 2700 do if isA162930 ( ithprime(i)) then printf("%d, ", ithprime(i)) ; fi; od: # R. J. Mathar, Jul 21 2009

MATHEMATICA

lst={}; Do[Do[AppendTo[lst, n^2+m^3], {n, 2*5!}], {m, 2*5!}]; lst=Sort[lst]; lst2={}; Do[If[lst[[n]]==lst[[n+1]]&&PrimeQ[lst[[n]]], AppendTo[lst2, lst[[n]]]], {n, Length[lst]-1}]; lst2;

CROSSREFS

Cf. A054402, A123364.

Sequence in context: A282378 A248400 A139947 * A138338 A267820 A200670

Adjacent sequences:  A162927 A162928 A162929 * A162931 A162932 A162933

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Jul 17 2009

EXTENSIONS

Slightly edited by R. J. Mathar, Jul 21 2009

STATUS

approved

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Last modified June 24 11:41 EDT 2021. Contains 345416 sequences. (Running on oeis4.)