This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A075348 Group the natural numbers such that the n-th group contains n terms and the group sum is the smallest possible prime: (2), (1, 4), (3, 5, 9), (6, 7, 8, 10), (11, 12, 13, 14, 17), (15, 16, 18, 19, 20, 21), ... yield the rows of this table. 6
 2, 1, 4, 3, 5, 9, 6, 7, 8, 10, 11, 12, 13, 14, 17, 15, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 32, 28, 29, 30, 31, 33, 34, 35, 37, 36, 38, 39, 40, 41, 42, 43, 44, 50, 45, 46, 47, 48, 49, 51, 52, 53, 54, 58, 55, 56, 57, 59, 60, 61, 62, 63, 64, 65, 71, 66, 67, 68, 69, 70, 72 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Row sums (the primes) are in A075345. In case of several possibilities to write the given prime, e.g. A075345(3) = 3+5+9 = 3+6+8, the lexicographically smallest is to be chosen, here (3,5,9) rather than (3,6,8). - M. F. Hasler, Sep 26 2015 The flattened triangle is a permutation of the positive integers with inverse = A262663 and fixed points A262665. LINKS Reinhard Zumkeller, Rows n = 1..100 of triangle, flattened FORMULA T(n,1)=A075346(n); T(n,n)=A075347(n); A075344(n)=sum(T(n,k): k=1..n). - Reinhard Zumkeller, Sep 26 2015 EXAMPLE Triangle starts: 2; 1,4; 3,5,9; 6,7,8,10; ... PROG (Haskell) import Data.List ((\\)) a075348 n k = a075348_tabl !! (n-1) !! (k-1) a075348_row n = a075348_tabl !! (n-1) a075348_tabl = f 0 [1..] where    f x zs = (us ++ [y]) : f (x + 1) (zs \\ (y : us)) where      y = g vs      g (w:ws) = if a010051' (sum us + w) == 1 then w else g ws      (us, vs) = splitAt x zs a075348_list = concat a075348_tabl -- Reinhard Zumkeller, Sep 26 2015 CROSSREFS Cf. A075345, A075346, A075347. Cf. A262663 (inverse), A262665 (fixed points). Sequence in context: A324755 A259019 A262663 * A326062 A055631 A234586 Adjacent sequences:  A075345 A075346 A075347 * A075349 A075350 A075351 KEYWORD nonn,tabl AUTHOR Amarnath Murthy, Sep 19 2002 EXTENSIONS Extended by Ray Chandler, Apr 09 2014 Name changed by M. F. Hasler, Sep 26 2015 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 19 23:01 EDT 2019. Contains 324222 sequences. (Running on oeis4.)