login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A294821 Irregular triangle read by rows: T(n,k) = 1 if k is the largest divisor of n <= sqrt(n), otherwise T(n,k) = 0. With n >= 1, and 1 <= k <= A000196(n). 1
1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1

COMMENTS

The first element of column k is in the row k^2.

LINKS

Table of n, a(n) for n=1..110.

FORMULA

T(n, A033676(n)) = 1.

T(n,k) = 0 if k is not equal to A033676(n), n >= 1, and 1 <= k <= A000196(n).

a(n) = A057427(A294721(n)).

EXAMPLE

Triangle begins:

1;

1;

1;

0, 1;

1, 0;

0, 1;

1, 0;

0, 1;

0, 0, 1;

0, 1, 0;

1, 0, 0;

0, 0, 1;

1, 0, 0;

0, 1, 0;

0, 0, 1;

0, 0, 0, 1;

1, 0, 0, 0;

0, 0, 1, 0;

1, 0, 0, 0;

0, 0, 0, 1;

0, 0, 1, 0;

0, 1, 0, 0;

1, 0, 0, 0;

0, 0, 0, 1;

0, 0, 0, 0, 1;

...

MATHEMATICA

Table[ReplacePart[ConstantArray[0, IntegerPart@ Sqrt@ n], SelectFirst[Reverse@ Divisors@ n, # <= Sqrt@ n &] -> 1], {n, 32}] // Flatten (* Michael De Vlieger, Nov 13 2017 *)

PROG

(PARI) row(n) = {d = divisors(n); kmax = vecmax(select(x->(x^2 <= n), d)); vector(sqrtint(n), k, k==kmax); }

tabf(nn) = for (n=1, nn, print(row(n))); \\ Michel Marcus, Dec 12 2017

CROSSREFS

Row n has length A000196(n).

Row sums give A000012.

Cf. A033676, A057427, A163280, A237273, A294721.

Sequences related to columns 1..12: A008578, A161344, A161345, A161424, A161835, A162527, A162527, A162528, A162529, A162530, A162531, A162532.

Sequence in context: A105589 A097806 A167374 * A132971 A085357 A011748

Adjacent sequences:  A294818 A294819 A294820 * A294822 A294823 A294824

KEYWORD

nonn,tabf

AUTHOR

Omar E. Pol, Nov 09 2017

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 21 18:45 EST 2019. Contains 320376 sequences. (Running on oeis4.)