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A050498 Arithmetic progressions of at least 4 terms with common difference 6 having the same value of phi(x) start at these numbers. 4
72, 216, 76326, 101526, 116646, 146886, 298086, 369366, 624966, 1375926, 1532166, 1558086, 1598406, 1750326, 1789206, 1866246, 1991526, 2516406, 2540886, 2620806, 2681286, 2827446, 3151446, 3196806, 3236406, 3489126 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

From Wolfdieter Lang, Jan 11 2021: (Start)

Conjecture: a(n) == 0 (mod 6) for n >= 1. After division by 6 the sequence becomes [12, 36, 12721, 16921, 19441, 24481, 49681, 61561, 104161, 229321, 255361, 259681, 266401, 291721, 298201, 311041, 331921, ...].

6*A163573 is a subsequence. See A163573 for the proof. Note that not all a(n), for n >= 3, are obtained by 6*A163573. The first such term is a(115) = 31850496, and a(115)/6 = 5308416 which is not a prime number, hence not a term of A163573. (End)

LINKS

Jud McCranie, Table of n, a(n) for n = 1..10000

EXAMPLE

phi(72) = phi(78) = phi(84) = phi(90) = 24, so 72 is in the sequence.

CROSSREFS

Cf. A000010, A039670, A163573.

Sequence in context: A204492 A204485 A344179 * A077535 A339994 A064716

Adjacent sequences:  A050495 A050496 A050497 * A050499 A050500 A050501

KEYWORD

nonn

AUTHOR

Jud McCranie, Dec 27 1999

STATUS

approved

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Last modified October 19 15:34 EDT 2021. Contains 348091 sequences. (Running on oeis4.)