This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
def a(n):
if (n==1) or (n%2 == 0) or (floor(2^(n/2+1))%2 != 0):
return 2^n + 1 + floor(2^(n/2+1))
else:
return 2^n + floor(2^(n/2+1)) # Robin Visser, Aug 17 2023
def a(n):
if n==2: return 10
elif (n%2 == 0): return 2^n + 1 + 2^(n/2+2)
elif ((floor(2^(n/2+1))%2 == 0) or (2^n-1).is_square()
or (4*2^n-3).is_square() or (4*2^n-7).is_square()):
if (frac(2^(n/2+1)) > ((sqrt(5)-1)/2)): return 2^n + 2*floor(2^(n/2+1))
else: return 2^n + 2*floor(2^(n/2+1)) - 1
else: return 2^n + 1 + 2*floor(2^(n/2+1)) # Robin Visser, Oct 01 2023
def a(n):
if (n==1) or (n%2 == 0) or (floor(2*3^(n/2))%3 != 0):
return 3^n + 1 + floor(2*3^(n/2))
else:
return 3^n + floor(2*3^(n/2)) # Robin Visser, Aug 17 2023
def a(n):
if n==2: return 20
elif (n%2 == 0): return 3^n + 1 + 4*3^(n/2)
elif ((floor(2*3^(n/2))%3 == 0) or (3^n-1).is_square()
or (4*3^n-3).is_square() or (4*3^n-7).is_square()):
if (frac(2*3^(n/2)) > ((sqrt(5)-1)/2)): return 3^n + 2*floor(2*3^(n/2))
else: return 3^n + 2*floor(2*3^(n/2)) - 1
else: return 3^n + 1 + 2*floor(2*3^(n/2)) # Robin Visser, Oct 01 2023
def a(n):
if (n==1) or (n%2 == 0) or (floor(2*5^(n/2))%5 != 0):
return 5^n + 1 + floor(2*5^(n/2))
else:
return 5^n + floor(2*5^(n/2)) # Robin Visser, Aug 17 2023
def a(n):
if (n%2 == 0): return 5^n + 1 + 4*5^(n/2)
elif ((floor(2*5^(n/2))%5 == 0) or (5^n-1).is_square()
or (4*5^n-3).is_square() or (4*5^n-7).is_square()):
if (frac(2*5^(n/2)) > ((sqrt(5)-1)/2)): return 5^n + 2*floor(2*5^(n/2))
else: return 5^n + 2*floor(2*5^(n/2)) - 1
else: return 5^n + 1 + 2*floor(2*5^(n/2)) # Robin Visser, Oct 01 2023