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.
%I A039670 #15 Aug 09 2017 23:41:22
%S A039670 72,78,84,90,216,222,228,234,76326,76332,76338,76344,101526,101532,
%T A039670 101538,101544,116646,116652,116658,116664,146886,146892,146898,
%U A039670 146904,298086,298092,298098,298104,369366,369372,369378,369384,624966,624972
%N A039670 Sets of 4 numbers in arithmetic progression with common difference 6 and whose phi values are equal.
%C A039670 This is really four sequences, not one! A050498 is a better version. - _N. J. A. Sloane_, Jan 01 2005
%D A039670 D. Wells, Curious and interesting numbers, Penguin Books, p. 112 (but beware errors).
%p A039670 with(numtheory):for n from 1 to 1000000 do if(phi(n)=phi(n+6) and phi(n+6)=phi(n+12) and phi(n+12)=phi(n+18)) then printf("%d, %d, %d, %d, ",n,n+6,n+12,n+18) fi od: # C. Ronaldo
%K A039670 nonn
%O A039670 1,1
%A A039670 _Felice Russo_
%E A039670 Corrected by _Jud McCranie_, Dec 26 1999
%E A039670 More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 29 2004