cp's OEIS Frontend

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.

A121898 Triangular numbers that are sandwiched between two semiprimes; or triangular numbers t such that t-1 and t+1 are both semiprime.

Table of values

n a(n)
1 120
2 300
3 528
4 780
5 2628
6 3240
7 3828
8 5460
9 13530
10 18528
11 19110
12 22578
13 25878
14 31878
15 32640
16 37128
17 49770
18 56280
19 64980
20 72390
21 73920
22 78210
23 103740
24 105570
25 115440
26 137550
27 159330
28 161028
29 277140
30 288420
31 316410
32 335790
33 370230
34 386760

List of values

[120, 300, 528, 780, 2628, 3240, 3828, 5460, 13530, 18528, 19110, 22578, 25878, 31878, 32640, 37128, 49770, 56280, 64980, 72390, 73920, 78210, 103740, 105570, 115440, 137550, 159330, 161028, 277140, 288420, 316410, 335790, 370230, 386760]

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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