cp's OEIS Frontend

A121281 Triangle T(n,k) read by rows: T(n,0) = A002110(n) and T(n,k) = A002110(n)/prime(k) for 1<=k<=n.

%I A121281 #16 Nov 20 2015 23:26:12
%S A121281 1,2,1,6,3,2,30,15,10,6,210,105,70,42,30,2310,1155,770,462,330,210,
%T A121281 30030,15015,10010,6006,4290,2730,2310,510510,255255,170170,102102,
%U A121281 72930,46410,39270,30030,9699690,4849845,3233230,1939938,1385670,881790,746130,570570,510510
%N A121281 Triangle T(n,k) read by rows: T(n,0) = A002110(n) and T(n,k) = A002110(n)/prime(k) for 1<=k<=n.
%H A121281 Reinhard Zumkeller, <a href="/A121281/b121281.txt">Rows n = 0..120 of triangle, flattened</a>
%F A121281 Sum_{0<=k<=n} T(n,k) = A024528(n).
%F A121281 T(n+1,k) = prime(n+1) * T(n,k) for k=0..n and T(n+1,n+1) = T(n,0). - _Reinhard Zumkeller_, Nov 20 2015
%e A121281 Triangle begins
%e A121281 1;
%e A121281 2, 1;
%e A121281 6, 3, 2;
%e A121281 30, 15, 10, 6;
%e A121281 210, 105, 70, 42, 30;
%o A121281 (PARI) tabl(nn) = {for (n=0, nn, pr = prod(i=1, n, prime(i)); for (k=0, n, if (k==0, v = pr, v = pr/prime(k)); print1(v, ", ");); print(););} \\ _Michel Marcus_, Apr 06 2015
%o A121281 (Haskell)
%o A121281 a121281 n k = a121281_tabl !! n !! k
%o A121281 a121281_row n = a121281_tabl !! n
%o A121281 a121281_tabl = [1] : f [1] a000040_list where
%o A121281    f xs@(x:_) (p:ps) = ys : f ys ps where ys = (map (* p) xs) ++ [x]
%o A121281 -- _Reinhard Zumkeller_, Nov 20 2015
%Y A121281 Cf. A000040, A002110, A024528, A070826.
%K A121281 nonn,tabl
%O A121281 0,2
%A A121281 _Philippe Deléham_, Aug 24 2006
%E A121281 Corrected and extended by _Michel Marcus_, Apr 06 2015