|
|
A102363
|
|
Triangle read by rows, constructed by a Pascal-like rule with left edge = 2^k, right edge = 2^(k+1)-1 (k >= 0).
|
|
6
|
|
|
1, 2, 3, 4, 5, 7, 8, 9, 12, 15, 16, 17, 21, 27, 31, 32, 33, 38, 48, 58, 63, 64, 65, 71, 86, 106, 121, 127, 128, 129, 136, 157, 192, 227, 248, 255, 256, 257, 265, 293, 349, 419, 475, 503, 511, 512, 513, 522, 558, 642, 768, 894, 978, 1014, 1023, 1024, 1025, 1035, 1080, 1200, 1410, 1662, 1872, 1992, 2037, 2047
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
COMMENTS
|
First column right of center divided by 3 equals powers of 4.
Right of left edge, sums of rows are divisible by 3.
Apparently the number of terms per row plus the number of numbers in natural order skipped per row equals a power of 2. - David Williams, Jun 27 2009
|
|
LINKS
|
|
|
FORMULA
|
G.f.: Sum_{n>=0} x^n * (1+x)^tr(n) = Sum_{n>=0} a(n)*x^n, where tr(n) = A002024(n+1) = floor(sqrt(2*n+1) + 1/2). - Paul D. Hanna, Feb 19 2016
G.f.: Sum_{n>=1} x^(n*(n-1)/2) * (1-x^n)/(1-x) * (1+x)^n = Sum_{n>=0} a(n)*x^n. - Paul D. Hanna, Feb 20 2016
|
|
EXAMPLE
|
This triangle begins:
1
2 3
4 5 7
8 9 12 15
16 17 21 27 31
32 33 38 48 58 63
64 65 71 86 106 121 127
128 129 136 157 192 227 248 255
256 257 265 293 349 419 475 503 511
G.f. of this sequence in flattened form:
A(x) = 1 + 2*x + 3*x^2 + 4*x^3 + 5*x^4 + 7*x^5 + 8*x^6 + 9*x^7 + 12*x^8 + 15*x^9 + 16*x^10 + 17*x^11 + 21*x^12 + 27*x^13 + 31*x^14 + 32*x^15 + ...
such that
A(x) = (1+x) + x*(1+x)^2 + x^2*(1+x)^2 + x^3*(1+x)^3 + x^4*(1+x)^3 + x^5*(1+x)^3 + x^6*(1+x)^4 + x^7*(1+x)^4 + x^8*(1+x)^4 + x^9*(1+x)^4 + x^10*(1+x)^5 + x^11*(1+x)^5 + x^12*(1+x)^5 + x^13*(1+x)^5 + x^14*(1+x)^5 + x^15*(1+x)^6 + ...
|
|
MAPLE
|
T:=proc(n, k) if k=0 then 2^n elif k=n then 2^(n+1)-1 else T(n-1, k)+T(n-1, k-1) fi end: for n from 0 to 10 do seq(T(n, k), k=0..n) od; # yields sequence in triangular form - Emeric Deutsch, Mar 26 2005
|
|
MATHEMATICA
|
t[n_, 0] := 2^n; t[n_, n_] := 2^(n+1)-1; t[n_, k_] := t[n, k] = t[n-1, k] + t[n-1, k-1]; Table[t[n, k], {n, 0, 10}, {k, 0, n}] // Flatten (* Jean-François Alcover, May 15 2013 *)
|
|
PROG
|
(PARI) /* Print in flattened form: Sum_{n>=0} x^n*(1+x)^tr(n) */
{tr(n) = ceil( (sqrt(8*n+9)-1)/2 )}
{a(n) = polcoeff( sum(m=0, n, x^m * (1+x +x*O(x^n))^tr(m) ), n)}
|
|
CROSSREFS
|
|
|
KEYWORD
|
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|