A162354 - OEIS

%I #8 Feb 18 2024 13:44:22

%S 3,19,109,163,307,523,613,631,1063,1117,1171,1567,1657,1693,1783,1801,

%T 1873,2017,2251,2269,2287,2521,2683,3061,3079,3169,3187,3457,3547,

%U 3691,3709,3907,4051,4357,4861,5077,5167,5347,5437,5563,5581,5653,5743,5851

%N Primes that are anagrams of triangular numbers.

%C 19 is an anagram of 91 = T(13) = 13*14/2.

%C 163, 613 and 631 are anagrams of 136 = T(16) = 16*17/2.

%H Michael S. Branicky, <a href="/A162354/b162354.txt">Table of n, a(n) for n = 1..10000</a>

%o (Python)

%o from sympy import primerange

%o from itertools import count, takewhile

%o def hash(n): return "".join(sorted(str(n)))

%o def aupto_digits(d):

%o     tris   = takewhile(lambda x:x<10**d, (i*(i+1)//2 for i in count(0)))

%o     primes = primerange(1, 10**d)

%o     T = set(map(hash, tris))

%o     return [p for p in primes if hash(p) in T]

%o print(aupto_digits(4)) # _Michael S. Branicky_, Feb 18 2024

%K nonn,base

%O 1,1

%A _Claudio Meller_, Jul 01 2009

%E Corrected by _Claudio Meller_, Jul 08 2009