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 A161205 Triangle read by rows in which row n lists 2n-1 followed by 2n numbers 2n. 15
 1, 2, 2, 3, 4, 4, 4, 4, 5, 6, 6, 6, 6, 6, 6, 7, 8, 8, 8, 8, 8, 8, 8, 8, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 15, 16, 16, 16, 16, 16, 16, 16, 16 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Row sums: A125202(n+1). - R. J. Mathar, Feb 16 2010 LINKS Omar E. Pol, Illustration: Divisors and pi(x) FORMULA If n is a perfect square, then a(n) = 2*sqrt(n)-1; otherwise a(n) = 2*floor(sqrt(n)). - Nathaniel Johnston, May 06 2011 a(n) = A000196(n-1) + A000196(n) = floor(sqrt(n-1)) + floor(sqrt(n)). - Ridouane Oudra, Jun 07 2019 EXAMPLE Triangle begins:   1,  2,  2;   3,  4,  4,  4,  4;   5,  6,  6,  6,  6,  6,  6;   7,  8,  8,  8,  8,  8,  8,  8,  8;   9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10; MAPLE A161205 := proc(n, k) if k=1 then 2*n-1; else 2*n; end if; end proc: seq(seq(A161205(n, k), k=1..2*n+1), n=1..12) ; # R. J. Mathar, Feb 16 2010 CROSSREFS Cf. A000005, A000720, A018253, A125202, A160811, A160812, A161339. Sequence in context: A003002 A087180 A029121 * A228942 A164531 A138161 Adjacent sequences:  A161202 A161203 A161204 * A161206 A161207 A161208 KEYWORD easy,nonn,tabf AUTHOR Omar E. Pol, Jun 19 2009 EXTENSIONS More terms from R. J. Mathar, Feb 16 2010 STATUS approved

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Last modified May 26 14:52 EDT 2020. Contains 334626 sequences. (Running on oeis4.)