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 A208855 Array of even catheti of primitive Pythagorean triangles when read by SW-NE diagonals. 4
 4, 12, 8, 20, 24, 12, 28, 40, 0, 16, 36, 56, 60, 48, 20, 44, 72, 84, 80, 60, 24, 52, 88, 0, 112, 0, 0, 28, 60, 104, 132, 144, 140, 120, 84, 32, 68, 120, 156, 176, 180, 168, 140, 96, 36, 76, 136, 0, 208, 220, 0, 0, 160, 0, 40 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS See the comments, reference and links in A208853. The present array is b(n,m) = 2*(2*n-1)*(2*m) if gcd((2*n-1,2*m)=1 and 0 otherwise. u=2*n-1, v=2*m. The array read by SW-NE diagonals is T(n,m):=b(n-m+1,m), n>=m>=1. All primitive Pythagorean triples are given by (a(n,m)=A208854(n,m),b(n,m),c(n,m)= A208853(n,m)), n>=1, m>=1. If the entry is 0 there is no primitive Pythagorean triple for these n and m values. LINKS Table of n, a(n) for n=1..55. FORMULA T(n,m)=b(n-m+1,m), n>=m>=1, with b(n,m):= 4*(2*n-1)*m if gcd((2*n-1,2*m)=1 and 0 otherwise. EXAMPLE Array b(n,m): ........m| 1 2 3 4 5 6 7 8 9 10 ... ........v| 2 4 6 8 10 12 14 16 18 20 n, u 1, 1 4 8 12 16 20 24 28 32 36 40 2, 3 12 24 0 48 60 0 84 96 0 120 3, 5 20 40 60 80 0 120 140 160 180 0 4, 7 28 56 84 112 140 168 0 224 252 280 5, 9 36 72 0 144 180 0 252 288 0 360 6, 11 44 88 132 176 220 264 308 352 396 440 7, 13 52 104 156 208 260 312 364 416 468 520 8, 15 60 120 0 240 0 0 420 480 0 0 9, 17 68 136 204 272 340 408 476 544 612 680 10,19 76 152 228 304 380 456 532 608 684 760 ... Triangle T(n,m): ......m| 1 2 3 4 5 6 7 8 9 10 ......v| 2 4 6 8 10 12 14 16 18 20 n, u 1, 1 4 2, 3 12 8 3, 5 20 24 12 4, 7 28 40 0 16 5, 9 36 56 60 48 20 6, 11 44 72 84 80 60 24 7, 13 52 88 0 112 0 0 28 8, 15 60 104 132 144 140 120 84 32 9, 17 68 120 156 176 180 168 140 96 36 10,19 76 136 0 208 220 0 0 160 0 40 ... For some triples see the example section of A208853. CROSSREFS Cf. A208853, A208854. Sequence in context: A310569 A145046 A205849 * A252984 A084415 A156681 Adjacent sequences: A208852 A208853 A208854 * A208856 A208857 A208858 KEYWORD nonn,easy,tabl AUTHOR Wolfdieter Lang, Mar 05 2012 STATUS approved

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Last modified November 30 23:40 EST 2023. Contains 367464 sequences. (Running on oeis4.)