This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A154722 Triangle read by rows in which row n lists: n, in the center of the row and the pairs of non-composite numbers that are equidistant to n, as shown below in the example. 13
 1, 1, 2, 3, 1, 3, 5, 1, 3, 4, 5, 7, 3, 5, 7, 1, 5, 6, 7, 11, 1, 3, 7, 11, 13, 3, 5, 8, 11, 13, 1, 5, 7, 9, 11, 13, 17, 1, 3, 7, 10, 13, 17, 19, 3, 5, 11, 17, 19, 1, 5, 7, 11, 12, 13, 17, 19, 23, 3, 7, 13, 19, 23, 5, 11, 14, 17, 23, 1, 7, 11, 13, 15 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Nathaniel Johnston, Table of n, a(n) for n = 1..5000 EXAMPLE Triangle begins: . . . . . . . . . . . . . . .1 . . . . . . . . . . . . . 1, 2, 3 . . . . . . . . . . . .1, .. 3, .. 5 . . . . . . . . . . 1, .. 3, 4, 5, .. 7 . . . . . . . . ... .. 3, .. 5, .. 7, .. . . . . . . . . 1, .. .. .. 5, 6, 7, .. .. .,11 . . . . . .1, .. 3, .. .. .. 7, .. .. ..11, ..13 . . . . .. .. 3, .. 5, .. .. 8, .. ..11, ..13, .. . . . .1, .. .. .. 5, .. 7, .. 9, ..11, ..13, .. .. ..17 . 1, .. 3, .. .. .. 7, .. .,10, .. ..13, .. .. ..17, ..19 MAPLE isnotcomp:=proc(n)return (n=1 or isprime(n)) end: for n from 1 to 10 do for k from 1 to 2*n-1 do if(k=n or (isnotcomp(k) and isnotcomp(2*n-k)))then print(k):fi:od:od: # Nathaniel Johnston, Apr 18 2011 CROSSREFS Cf. A000040, A008578, A154720, A154721, A154723, A154724, A154725, A154726, A154727. Sequence in context: A185311 A214582 A050375 * A194760 A035517 A099471 Adjacent sequences:  A154719 A154720 A154721 * A154723 A154724 A154725 KEYWORD easy,nonn,tabf AUTHOR Omar E. Pol, Jan 14 2009 EXTENSIONS a(45) - a(73) from Nathaniel Johnston, Apr 18 2011 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 .