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URL: https://oeis.org/A273185

⇱ A273185 - OEIS

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A273185
Start with a(0) = 0. Thereafter a(n) is the number of m < n with the property that a(m) + n is a perfect square.
2
0, 1, 0, 1, 2, 0, 0, 1, 3, 4, 0, 0, 1, 1, 1, 6, 6, 0, 0, 2, 0, 1, 1, 2, 8, 9, 0, 1, 1, 0, 2, 0, 1, 1, 4, 12, 12, 2, 0, 0, 1, 1, 0, 2, 0, 2, 1, 7, 15, 17, 0, 0, 2, 0, 0, 1, 1, 1, 2, 0, 2, 1, 10, 19, 22, 0, 1, 0, 0, 2, 0, 1, 1, 1, 1, 2, 0, 2, 2, 14
OFFSET
0,5
EXAMPLE
a(3) = 1 because 3 + a(1) is a perfect square.
a(4) = 2 because 4 + a(0) and 4 + a(2) are perfect squares.
MATHEMATICA
a = {0}; Do[AppendTo[a, Count[a + n, k_ /; IntegerQ@ Sqrt@ k]], {n, 79}]; a (* Michael De Vlieger, May 25 2016 *)
PROG
(Java)
int n = 1000;
int[] terms = new int[n];
for (int i = 0; i < n; i++) {
for (int j = 0; j < i; j++) {
if (Math.sqrt(i+terms[j]) == Math.floor(Math.sqrt(i+terms[j]))) {
terms[i]++;
}
}
System.out.print(terms[i] + ", ");
}
CROSSREFS
Cf. A273190.
Sequence in context: A307968 A338501 A242464 * A375467 A373183 A351776
KEYWORD
easy,nonn
AUTHOR
Alec Jones, May 17 2016
STATUS
approved