A138594 - OEIS

%I #8 Mar 11 2016 21:23:38

%S 15,21,27,28,33,35,36,39,42,44,45,49,51,52,54,55,56,57,60,63,65,66,68,

%T 69,70,72,75,76,77,78,81,84,85,87,88,90,91,92,93,95,98,99,100,102,104,

%U 105,108,110,111,112,114,115,116,117,119,120,121,123,124,125,126,129

%N Sums of 6 or more consecutive nonnegative integers.

%C Also, the numbers of the form s*k+A000217(k-1), s>=0, k>=6. [From _R. J. Mathar_, Jul 31 2008]

%H Robert Israel, <a href="/A138594/b138594.txt">Table of n, a(n) for n = 1..10000</a>

%e 0+1+2+3+4+5=15, 1+2+3+4+5+6=21, 2+3+4+5+6+7=27, 1+2+3+4+5+6+7=28, ...

%p N:= 1000: # to get all terms <= N

%p sort(convert({seq(seq(b*(2*a+b-1)/2, a=0..floor(N/b - (b+1)/2)),

%p b=6..floor((sqrt(1+8*N)-1)/2))},list)); # _Robert Israel_, Mar 11 2016

%t Array[r,9];k=0;For[i=0,i<=77,a=i*5+10;For[j=i+5,j<=77,a=a+j;k++;r[k]=a;j++ ];i++ ];q=Union[Array[r,k]];StringTake[ToString[q],123]

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, May 13 2008

%E More terms from _Vladimir Joseph Stephan Orlovsky_, Mar 07 2010

%E Name edited by _Robert Israel_, Mar 11 2016