This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A256230 Numbers n such that neither n nor 2*n is representable as x*y+x+y, where x>=y>1. 0
 0, 1, 2, 3, 5, 6, 9, 18, 21, 30, 33, 36, 78, 81, 96, 105, 138, 141, 156, 165, 198, 210, 228, 261, 270, 273, 306, 330, 336, 345, 366, 378, 393, 438, 453, 498, 525, 546, 561, 576, 585, 600, 606, 618, 660, 690, 726, 765, 810, 828, 861, 876, 933, 936, 966, 996, 1005, 1008 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS PROG (Python) TOP = 2200 a = [0]*TOP for y in xrange(2, TOP/2):   for x in xrange(y, TOP/2):     k = x*y + x + y     if k>=TOP: break     a[k]=1 print [n for n in xrange(TOP/2) if a[n]==0 and a[2*n]==0] CROSSREFS Cf. A254636, A255362. Cf. A064238 (also 3*n cannot be represented as x*y+x+y, x>=y>1). Cf. A237189 (also 3*n and 4*n cannot be represented as x*y+x+y, x>=y>1). Sequence in context: A240555 A102694 A124253 * A079371 A131761 A272776 Adjacent sequences:  A256227 A256228 A256229 * A256231 A256232 A256233 KEYWORD nonn AUTHOR Alex Ratushnyak, Mar 19 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 | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 18 00:19 EST 2019. Contains 320237 sequences. (Running on oeis4.)