This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A099468 Numbers n such that there are no primes < 2n in the sequence m(0)=n, m(k+1)=m(k)+4k. 1
 1, 21, 45, 51, 81, 213, 249, 315, 477, 525, 681, 891, 1143, 1221, 1851, 1965, 2415, 5133 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS No others < 10^8. Note that 3 divides all these n > 1. This sequence is conjectured to be complete. Related to a question posed in A036468 by Zhang Ming-Zhi. Let r=2s+1 be an odd number. If n = (s+1)^2+s^2, then the sequence m(0)=n, m(k+1)=m(k)+4k for k=0,1,...s calculates the s+1 distinct sums of two squares (r-i)^2+i^2. LINKS EXAMPLE 45 is here because 45, 49, 57, 69 and 85 are all composite. MATHEMATICA lst={}; Do[n=m; found=False; k=0; While[n=n+4k; !found && n<2m, found=PrimeQ[n]; k++ ]; If[ !found, AppendTo[lst, m]], {m, 1, 10000, 2}]; lst CROSSREFS Cf. A036468 (number of ways to represent 2n+1 as a+b with a^2+b^2 prime). Sequence in context: A180857 A168519 A003857 * A063500 A102603 A147222 Adjacent sequences:  A099465 A099466 A099467 * A099469 A099470 A099471 KEYWORD nonn AUTHOR T. D. Noe, Oct 17 2004 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .