A355237 First occurrence of difference n between two consecutive terms of A000404. a(n) gives the lower term. The upper term is A355238.

17, 8, 2, 13, 20, 74, 90, 137, 377, 3050, 986, 1669, 4181, 6530, 1493, 8434, 9704, 22160, 10709, 5165, 16109, 154708, 58418, 31657, 52393, 401480, 176810, 101349, 105572, 678356, 241882, 501716, 393817, 284002, 685541, 1437353, 1751296, 3225578, 3439258, 2479594

Offset

1,1

Links

Table of n, a(n) for n=1..40.

Formula

a(n) = A355238(n) - n.

Prog

(Python)
from itertools import count
from sympy import factorint
def A355237(n):
    m = 2
    for k in count(2):
        c = False
        for p in (f:=factorint(k)):
            if (q:= p & 3)==3 and f[p]&1:
                break
            elif q == 1:
                c = True
        else:
            if c or f.get(2, 0)&1:
                if k-m == n:
                    return m
                m = k # Chai Wah Wu, Jul 01 2022

Crossrefs

Cf. A000404, A104271, A355238.

Sequence in context: A356060 A048368 A040275 * A033337 A122063 A083308

Adjacent sequences: A355234 A355235 A355236 * A355238 A355239 A355240

Keyword

nonn

Author

Hugo Pfoertner, Jun 30 2022

Status

approved