A365239 Locations of records in A365196.

0, 1, 9, 13, 57, 69, 81, 1005, 1485, 30045, 32865, 40845, 59565, 114345, 262185, 340725, 386925, 396825, 611325, 1211925

Offset

1,3

Comments

a(n) is odd for n >= 2.

a(n) is divisible by 15 for n >= 8.

Links

Table of n, a(n) for n=1..20.

Formula

A365196(a(n)) = A364455(n).

Example

a(1) = 0 with A365196(0) = 2 is the first term of A365196.
a(2) = 1 because A365196(1) = 3 is the first term of A365196 greater than 2.
a(3) = 9 because A365196(9) = 4 is the first term of A365196 greater than 3.

Maple

f:= proc(k) local j;
  for j from 0 do if not numtheory:-issqrfree(2^j+k) then return j fi
  od;
end proc:
A:= 0:  m:= 2: count:= 1:
for i from 1 by 2 while count < 19 do
  if i mod 3 <> 0 and m >= 6 then next fi;
  if i mod 5 <> 0 and m >= 20 then next fi;
  v:= f(i);
  if v > m then A:= A, i; m:= v; count:= count+1;  fi;
od:
A;

Mathematica

r = 0; Reap[Do[k = 0; While[SquareFreeQ[2^k + i], k++]; If[k > r, Sow[i]; r = k], {i, 0, 270000}] ][[-1, 1]] (* Michael De Vlieger, Aug 27 2023 *)

Crossrefs

Cf. A364455, A365196.

Sequence in context: A270679 A270903 A270936 * A271006 A271052 A305650

Adjacent sequences: A365236 A365237 A365238 * A365240 A365241 A365242

Keyword

nonn,more

Author

Robert Israel, Aug 27 2023

Status

approved