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 A154722 Triangle read by rows in which row n lists: n, in the center of the row and the pairs of noncomposite 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: A214582 A050375 A300724 * 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

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Last modified January 19 19:49 EST 2019. Contains 319309 sequences. (Running on oeis4.)