cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A281292 Squarefree numbers that are the sum of two squares in exactly one way.

Original entry on oeis.org

1, 2, 5, 10, 13, 17, 26, 29, 34, 37, 41, 53, 58, 61, 73, 74, 82, 89, 97, 101, 106, 109, 113, 122, 137, 146, 149, 157, 173, 178, 181, 193, 194, 197, 202, 218, 226, 229, 233, 241, 257, 269, 274, 277, 281, 293, 298, 313, 314, 317, 337, 346, 349, 353, 362, 373, 386, 389, 394, 397
Offset: 1

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Author

Thomas Ordowski, Jan 19 2017

Keywords

Comments

Numbers of the form x^2 + y^2 with gcd(x, y) = 1 that have no other decompositions into a sum of two squares.
Numbers 1 and 2 together with p and 2p, where prime p == 1 (mod 4).
Conjecture: each positive integer is a sum |x| + |y| such that x^2 + y^2 is in the sequence.
Numbers in A020893 but not in A274044. - Wolfdieter Lang, Jan 28 2017

Examples

			1 = 0^2 + 1^2 and 2 = 1^1 + 1^2.
p = x^2 + y^2 and 2p = (y-x)^2 + (x+y)^2.

Links

Crossrefs

Cf. A002144, A020893, A274044.

Programs

Formula

a(n) ~ C n log n, where C = 4/3. - Charles R Greathouse IV, Feb 01 2017, corrected by Thomas Ordowski, Feb 10 2017
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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