OFFSET
1,1
COMMENTS
Is a(n) >= c*n^e for some constants c and e? For terms in the b-file, we'd have e > 2.1598. - David A. Corneth, Mar 15 2019
LINKS
David A. Corneth, Table of n, a(n) for n = 1..14685 (Terms <= 10^9)
Bundeswettbewerb Mathematik 2017, Die Aufgaben der 2. Runde 2017
Bundeswettbewerb Mathematik 2017, Aufgaben und Lösungen 2. Runde 2017
David A. Corneth, PARI program
EXAMPLE
126 and 127 are terms because: 126 = 1^2 + 5^3, 127 = 10^2 + 3^3, 128 = 8^2 + 4^3, 129 = 11^2 + 2^3. - Bernard Schott, Mar 17 2019
MATHEMATICA
s = Union@ Flatten@ Table[s^2 + c^3, {s, 141}, {c, 27}]; First@# & /@ Select[Partition[s, 3, 1], #[[1]] + 2 == #[[3]] &] (* Robert G. Wilson v, Jan 07 2018 *)
With[{mx=19000}, Select[Partition[Union[Flatten[Table[a^2+b^3, {a, Ceiling[ Sqrt[mx]]}, {b, Ceiling[Surd[mx, 3]]}]]], 3, 1], Differences[#]=={1, 1}&]][[All, 1]] (* Harvey P. Dale, Sep 07 2020 *)
PROG
(PARI) is_a055394(n) = for(k=1, sqrtnint(n-1, 3), if(issquare(n-k^3), return(1))); 0 \\ after Charles R Greathouse IV
is(n) = is_a055394(n) && is_a055394(n+1) && is_a055394(n+2) \\ Felix Fröhlich, Jan 08 2018
(PARI) See Corneth Link \\ David A. Corneth, Mar 15 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
David A. Corneth, Dec 30 2017
STATUS
approved