27501 is a member of OEIS A295689: a(n) = a(n-1) + a(n-3) + a(n-4), where a(0) = 2, a(1) = 0, a(2) = 2, a(3) = 1. The sequence can be generated as follows:

INPUT

a,b,c,d = 2,0,2,1

L=[a,b,c,d]

for n in [1..20]:

  e=d+b+a

  L.append(e)

  a,b,c,d=b,c,d,e

print(L)

OUTPUT

[2, 0, 2, 1, 3, 5, 8, 12, 20, 33, 53, 85, 138, 224, 362, 585, 947, 1533, 2480, 4012, 6492, 10505, 16997, 27501]

OEIS comments: a(n)/a(n-1) -> (1 + sqrt(5))/2 = golden ratio (A001622), so that a( ) has the growth rate of the Fibonacci numbers (A000045).

27501 is the 89-th nonagonal number.

27501 is a happy, sphenic and lucky number.

27501 can be rendered as a digit equation as follows:

(2 + 7 + 5) ^ 0 = 1 or -2 + 7 -5 = 0 * 1