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

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A166596 Smallest triangular number with exactly n anagrams that are triangular numbers. 1
0, 120, 4095, 36046, 147153, 219453, 1021735, 1053426, 104653, 10149765, 10294453, 10348975, 100486576, 10725396, 103428153, 20759346, 12347965, 100174935, 129548656, 102968425, 104697685, 102925378, 160249753, 123865930, 126047503, 102538360, 224073865 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..10000 (terms 1..46 from Chai Wah Wu)
EXAMPLE
n=1, {0} (triangular number with no nontrivial anagram)
n=2, {120,210} (two anagrams of triangular numbers)
n=3, {4095,4950,9045} (three anagrams of triangular numbers)
n=4, {36046,43660,46360,66430} (four anagrams of triangular numbers)
n=5, {147153,375411,435711,713415,741153}
n=6, {219453,243951,432915,493521,539241,943251}
n=7, {1021735,1710325,2310175,2375110,3201715,5312170,7321051}
n=8, {1053426,1345620,1360425,1405326,1624503,2465310,5643120,6503421}
n=9, {104653,135460,354061,403651,406351,431056,465130,534061,634501}
n=10, {10149765,14609715,15149760,16974051,17461095,17609145,41509716,41591760, 41756091,61710495}.
PROG
(Python)
from math import isqrt
from collections import Counter
from itertools import count, islice, combinations_with_replacement as mc
def tris(d): # generator of triangular numbers with d digits
ilb, lb, ub = isqrt(2*10**(d-1))-1, 10**(d-1), 10**d
if d == 1: yield 0
for i in count(ilb):
t = i*(i+1)//2
if t < lb: continue
elif t >= ub: break
yield t
def agen(): # generator of sequence terms
n, adict = 1, dict()
for d in count(1):
c = Counter("".join(sorted(str(t))) for t in tris(d))
for t in tris(d):
v = c["".join(sorted(str(t)))]
if v not in adict: adict[v] = t
while n in adict: yield adict[n]; n += 1
print(list(islice(agen(), 46))) # Michael S. Branicky, Feb 18 2024
CROSSREFS
Cf. A034291 Triangular numbers that have some nontrivial permutation of digits which is also triangular.
Sequence in context: A231136 A222003 A139389 * A000514 A179060 A342073
KEYWORD
base,nonn
AUTHOR
Zak Seidov, Oct 17 2009
STATUS
approved

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 16:34 EDT 2024. Contains 371254 sequences. (Running on oeis4.)