The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A203071 Triangle read by antidiagonals: T[r+1,c] = T[r,c]+T[r,c+1], but only nonprime numbers may be used. 2

%I

%S 1,8,9,4,12,21,14,18,30,51,6,20,38,68,119,10,16,36,74,142,261,22,32,

%T 48,84,158,300,561,27,49,81,129,213,371,671,1232,15,42,91,172,301,514,

%U 885,1556,2788,35,50,92,183,355,656,1170,2055,3611,6399,40,75,125,217,400,755,1411,2581,4636

%N Triangle read by antidiagonals: T[r+1,c] = T[r,c]+T[r,c+1], but only nonprime numbers may be used.

%C This sequence is the lexicographically earliest one satisfying the given constraint. It is built using the smallest possible choice for the next term [of the first row A203072] not leading to a contradiction.

%C Is this a permutation of the nonprimes?

%H Lars Blomberg, <a href="/A203071/b203071.txt">Table of n, a(n) for n = 1..20100 (the first 200 antidiagonals)</a>

%e row 1: 1 8 4 14 6 10 22 27 15 ... [A203072]

%e row 2: 9 12 18 20 16 32 49 42 ...

%e row 3: 21 30 38 36 48 81 91 ...

%e row 4: 51 68 74 84 129 172 ...

%e row 5: 119 142 158 213 301 ...

%e row 6: 261 300 371 514 ...

%e row 7: 561 671 885 ...

%e row 8: 1232 1556 ...

%e row 9: 2788 ...

%o (PARI) list_by_antidiagonals(a)={my(u=[]);for(i=1,#a,u=concat(u,a[i]);forstep(j=i-1,1,-1,u=concat(u,a[j]+=a[j+1])));u} /* requires the first line as input */

%K nonn,tabl

%O 1,2

%A _Eric Angelini_, Dec 28 2011

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

Last modified December 8 01:51 EST 2022. Contains 358672 sequences. (Running on oeis4.)