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 A064865 Fill a triangular array by rows by writing numbers 1, then 1 up to 2^2, then 1 up to 3^2, then 1 up to 4^2 and so on. The final elements of the rows form the sequence. 17
 1, 2, 1, 5, 1, 7, 14, 6, 15, 25, 11, 23, 36, 14, 29, 45, 13, 31, 50, 6, 27, 49, 72, 15, 40, 66, 93, 21, 50, 80, 111, 22, 55, 89, 124, 16, 53, 91, 130, 1, 42, 84, 127, 171, 20, 66, 113, 161, 210, 35, 86, 138, 191, 245, 44, 100, 157, 215, 274, 45, 106, 168, 231, 295, 36 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Does every number appear at least once? Do some numbers like 1 appear infinitely often? - Robert G. Wilson v, Oct 10 2001 Difference between n-th triangular number and largest square pyramidal number (A000330) less than it. - Franklin T. Adams-Watters, Sep 11 2006 LINKS Alois P. Heinz, Table of n, a(n) for n = 1..10000 FORMULA a(n) = n(n+1)/2 - max_{p(m) < n(n+1)/2} p(m), where p(m) = m(m+1)(2m+1)/6. - Franklin T. Adams-Watters, Sep 11 2006 EXAMPLE The triangle begins: ....1 ...1.2 ..3.4.1 .2.3.4.5 6.7.8.9.1 MATHEMATICA a = {}; Do[a = Append[a, Table[i, {i, 1, n^2} ]], {n, 1, 100} ]; a = Flatten[a]; Do[Print[a[[n(n + 1)/2]]], {n, 1, 100} ] CROSSREFS Table: A064866. Cf. A000217, A000330. Sequence in context: A263454 A036073 A124227 * A178472 A331888 A178470 Adjacent sequences:  A064862 A064863 A064864 * A064866 A064867 A064868 KEYWORD easy,nonn AUTHOR Floor van Lamoen, Oct 08 2001 EXTENSIONS More terms from Robert G. Wilson v, Oct 10 2001 STATUS approved

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Last modified April 3 04:21 EDT 2020. Contains 333195 sequences. (Running on oeis4.)