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 A061885 n + largest triangular number less than or equal to n. 5
 0, 2, 3, 6, 7, 8, 12, 13, 14, 15, 20, 21, 22, 23, 24, 30, 31, 32, 33, 34, 35, 42, 43, 44, 45, 46, 47, 48, 56, 57, 58, 59, 60, 61, 62, 63, 72, 73, 74, 75, 76, 77, 78, 79, 80, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 132 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(9)=9+6=15; a(10)=10+10=20; a(11)=11+10=21. LINKS _Reinhard Zumkeller_, Table of n, a(n) for n = 0..10000 FORMULA a(n) = n+A057944(n) = 2n-A002262(n) = n+[(sqrt(1+8*n)-1)/2]*[(sqrt(1+8*n)+1)/2]/2. a(n) = A004201(n+1) - 1. [From Franklin T. Adams-Watters, Jul 05 2009] PROG (Haskell) a061885 n = n + a057944 n  -- Reinhard Zumkeller, Feb 03 2012 CROSSREFS Cf. A060985. Sequence in context: A069579 A065193 A116047 * A138683 A072426 A189137 Adjacent sequences:  A061882 A061883 A061884 * A061886 A061887 A061888 KEYWORD nonn AUTHOR Henry Bottomley, May 12 2001 STATUS approved

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