The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A258366 Numbers n representable as x*y + x + y, where x >= y > 1, such that all x's and y's in all representation(s) of n are perfect squares. 0
 24, 49, 84, 184, 288, 504, 628, 984, 1284, 1368, 1716, 2004, 2884, 3348, 3384, 3736, 4368, 6484, 6816, 7288, 8004, 9508, 9808, 10200, 11508, 14584, 14836, 15684, 19896, 21348, 21784, 22048, 25048, 25956, 27216, 27384, 35284, 38808, 40500, 40504, 44184, 47988, 49588, 50628 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A subsequence of A254671. Is 49 the only odd term? LINKS Table of n, a(n) for n=1..44. EXAMPLE 24 = 4*4 + 4 + 4. 49 = 9*4 + 9 + 4, and because this is the only representation, 49 is in the sequence. 129 = 4*25+25+4 = 12*9 + 12 + 9, and because 12 is not a square, 129 is not a term. PROG (Python) def isqrt(a): sr = 1 << (int.bit_length(int(a)) >> 1) while a < sr*sr: sr>>=1 b = sr>>1 while b: s = sr+b if a >= s*s: sr = s b>>=1 return sr def isSquare(a): sr = isqrt(a) return a==sr*sr TOP = 100000 a = [0]*TOP no= [0]*TOP for y in range(2, TOP//2): for x in range(y, TOP//2): k = x*y + x + y if k>=TOP: break if no[k]==0: a[k]=1 if not (isSquare(x) and isSquare(y)): no[k]=1 print([n for n in range(TOP) if a[n]>0 and no[n]==0]) CROSSREFS Cf. A254671, A256073, A000290. Sequence in context: A044101 A044482 A045294 * A195158 A045279 A042142 Adjacent sequences: A258363 A258364 A258365 * A258367 A258368 A258369 KEYWORD nonn AUTHOR Alex Ratushnyak, May 27 2015 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 14 15:29 EDT 2024. Contains 375165 sequences. (Running on oeis4.)